OSPF distribute-list example (Block Lists)

lated routers under Dynamips / Dynagen / GNS3. Network diagram was exported from the running GNS3 model.


[edit] Base device configurations
[edit] R0 (172.16.0.1)
version 12.4
!
hostname R0
!
ip cef
no ip domain lookup
!
interface Loopback0
ip address 172.16.0.1 255.255.255.255
!
interface FastEthernet0/0
ip address 10.1.0.1 255.255.255.252
duplex auto
speed auto
!
end
[edit] R1 (172.16.0.2)
version 12.4
!
hostname R2
!
ip cef
no ip domain lookup
!
interface Loopback0
ip address 172.16.0.2 255.255.255.255
!
interface FastEthernet0/0
ip address 10.1.0.2 255.255.255.252
duplex auto
speed auto
!
interface FastEthernet1/0
ip address 10.2.0.1 255.255.255.252
duplex auto
speed auto
!

end
[edit] R3 (172.16.0.3)
version 12.4
!
hostname R3
!
ip cef
no ip domain lookup
!
interface Loopback0
ip address 172.16.0.3 255.255.255.255
!
interface Loopback1
ip address 192.168.1.1 255.255.255.0
!
interface FastEthernet0/0
ip address 10.2.0.2 255.255.255.252
duplex auto
speed auto
!
end
[edit] OSPF distribute-list example (Block Lists)
[edit] Base OSPF Configuration, without block lists
[edit] R0 (172.16.0.1)
router ospf 1
router-id 172.16.0.1
log-adjacency-changes
network 10.1.0.0 0.0.0.3 area 0
network 172.16.0.1 0.0.0.0 area 0
!
[edit] R1 (172.16.0.2)
router ospf 1
router-id 172.16.0.2
log-adjacency-changes
network 10.1.0.0 0.0.0.3 area 0
network 10.2.0.0 0.0.0.3 area 0
network 172.16.0.2 0.0.0.0 area 0
!
[edit] R2 (172.16.0.3)
router ospf 1
router-id 172.16.0.3
redistribute connected subnets metric-type 1
log-adjacency-changes
network 10.2.0.0 0.0.0.3 area 0
network 172.16.0.3 0.0.0.0 area 0
!
Router R2 is redistributing the loopback adapter 192.168.1.0 into OSPF in order to generate an LSA Type 5 (area-filters must be used for LSA type 3s). The route makes it from router R2, to R1, to R0. See the routing output below, important information highlighted.
[edit] OSPF Standard routing - no distribute-list
[edit] R0 show ip route example – OSPF Standard routing
R0#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

172.16.0.0/32 is subnetted, 3 subnets
C 172.16.0.1 is directly connected, Loopback0
O 172.16.0.2 [110/2] via 10.1.0.2, 00:00:00, FastEthernet0/0
O 172.16.0.3 [110/3] via 10.1.0.2, 00:00:00, FastEthernet0/0
10.0.0.0/30 is subnetted, 2 subnets
O 10.2.0.0 [110/2] via 10.1.0.2, 00:00:00, FastEthernet0/0
C 10.1.0.0 is directly connected, FastEthernet0/0
192.168.1.0/32 is subnetted, 1 subnets
O 192.168.1.1 [110/3] via 10.1.0.2, 00:00:00, FastEthernet0/0
[edit] R0 show ospf database – OSPF Standard routing
R0#sh ip ospf database
OSPF Router with ID (172.16.0.1) (Process ID 1)

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count
172.16.0.1 172.16.0.1 1284 0x80000004 0x008449 2
172.16.0.2 172.16.0.2 1346 0x80000002 0x00A4FB 3
172.16.0.3 172.16.0.3 419 0x80000006 0x00D6E8 2

Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum
10.1.0.1 172.16.0.1 1350 0x80000001 0x00E70F
10.2.0.2 172.16.0.3 1347 0x80000001 0x00D917

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag
192.168.1.0 172.16.0.3 411 0x80000001 0x00F009 0
[edit] R1 show ip route example – OSPF Standard Config
R1#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

172.16.0.0/32 is subnetted, 3 subnets
O 172.16.0.1 [110/2] via 10.1.0.1, 00:01:32, FastEthernet0/0
C 172.16.0.2 is directly connected, Loopback1
O 172.16.0.3 [110/2] via 10.2.0.2, 00:01:32, FastEthernet1/0
10.0.0.0/30 is subnetted, 2 subnets
C 10.2.0.0 is directly connected, FastEthernet1/0
C 10.1.0.0 is directly connected, FastEthernet0/0
192.168.1.0/30 is subnetted, 1 subnets
O E1 192.168.1.0 [110/21] via 10.2.0.2, 00:01:32, FastEthernet1/0
[edit] R1 show ip ospf database example – OSPF Standard Config
R1# sh ip ospf database

OSPF Router with ID (172.16.0.2) (Process ID 1)

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count
172.16.0.1 172.16.0.1 984 0x80000004 0x008449 2
172.16.0.2 172.16.0.2 1044 0x80000002 0x00A4FB 3
172.16.0.3 172.16.0.3 117 0x80000006 0x00D6E8 2

Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum
10.1.0.1 172.16.0.1 1050 0x80000001 0x00E70F
10.2.0.2 172.16.0.3 1045 0x80000001 0x00D917

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag
192.168.1.0 172.16.0.3 109 0x80000001 0x00F009 0

We can see in the above examples, R2 generates a route and it propagates to R1. All routers along the path have this entry in their OSPF Configuration.
[edit] Adding the Distribute-list (Block List) to OSPF
In OSPF, the distribute-command should be defined as only a mechanism as to whether or not the specific router the distribute-list is configured on accepts a route for insertion into it’s own OSPF table. One of the key points to remember about OSPF is that it’s about global database consistency. Every device must have the same view of the entire topology of the network. Every router knows how to get everywhere else. This functionality is different than EIGRP, as it will be shown below. The distribute-list command on OSPF only tells OSPF which routes it can put in the FIB.
[edit] R1 configuration
router ospf 1
router-id 172.16.0.2
log-adjacency-changes
network 10.1.0.0 0.0.0.3 area 0
network 10.2.0.0 0.0.0.3 area 0
network 172.16.0.2 0.0.0.0 area 0
distribute-list 50 in FastEthernet1/0
!
access-list 50 deny 192.168.1.0 0.0.0.255
access-list 50 permit any
!
The only difference here is that an access-list is applied to the distribute-list statements.
[edit] R1 show ip route example – OSPF Distribute-list applied
We can see in the output below that R1 does not actually have 192.168.1.0/24 in it’s IP routing table. The distribute-list command on R1 blocks this route.
R1# sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

172.16.0.0/32 is subnetted, 3 subnets
O 172.16.0.1 [110/2] via 10.1.0.1, 00:00:16, FastEthernet0/0
C 172.16.0.2 is directly connected, Loopback1
O 172.16.0.3 [110/2] via 10.2.0.2, 00:00:16, FastEthernet1/0
10.0.0.0/30 is subnetted, 2 subnets
C 10.2.0.0 is directly connected, FastEthernet1/0
C 10.1.0.0 is directly connected, FastEthernet0/0
*******192.168.1.0/24 is MISSING*****
[edit] R1 show ip ospf database example – OSPF Distribute-list applied
The distribute-list command only removes the route from the OSPF Table – it does not stop that route from being advertised out to other OSPF Neighbors. This is for database consistencies sake.
R1#sh ip ospf database

OSPF Router with ID (172.16.0.2) (Process ID 1)

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count
172.16.0.1 172.16.0.1 1164 0x80000004 0x008449 2
172.16.0.2 172.16.0.2 1224 0x80000002 0x00A4FB 3
172.16.0.3 172.16.0.3 297 0x80000006 0x00D6E8 2

Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum
10.1.0.1 172.16.0.1 1230 0x80000001 0x00E70F
10.2.0.2 172.16.0.3 1225 0x80000001 0x00D917

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag
192.168.1.0 172.16.0.3 289 0x80000001 0x00F009 0
[edit] R1 debug ip ospf spf/tree
Debugging OSPF spf and tree events shows below that LSAs are still generated for 192.168.1.0/24 even though a distribute-list is applied, and that route is still added to the database. Router R1 specifically just chooses not to route for it.
*Mar 1 02:54:36.799: OSPF: Started Building Type 5 External Routes
*Mar 1 02:54:36.803: OSPF: Start processing Type 5 External LSA 192.168.1.0, mask 255.255.255.252, adv 172.16.0.3, age 1905, seq 0x80000001, metric 20, metric-type 1
*Mar 1 02:54:36.803: Add better path to LSA ID 192.168.1.0, gateway 10.2.0.2, dist 21
*Mar 1 02:54:36.803: Add path: next-
R1#hop 10.2.0.2, interface FastEthernet1/0
*Mar 1 02:54:36.803: network update dest_addr 192.168.1.0 mask 255.255.255.252 gateway 10.2.0.2
*Mar 1 02:54:36.807: OSPF: insert route list LS ID 192.168.1.0, type 5, adv rtr 172.16.0.3
[edit] R0 show ip route example – OSPF distribute-list applied
We can see here below that 192.168.1.0 is added to the routing table, with the next-hop IP of R1. You may expect that this route to not enter the OSPF Table, but remember, distribute-list only changes the FIB (forwarding information base) table on the local router it is configured on.
R0#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

172.16.0.0/32 is subnetted, 3 subnets
C 172.16.0.1 is directly connected, Loopback0
O 172.16.0.2 [110/2] via 10.1.0.2, 00:03:58, FastEthernet0/0
O 172.16.0.3 [110/3] via 10.1.0.2, 00:03:58, FastEthernet0/0
10.0.0.0/30 is subnetted, 2 subnets
O 10.2.0.0 [110/2] via 10.1.0.2, 00:03:58, FastEthernet0/0
C 10.1.0.0 is directly connected, FastEthernet0/0
192.168.1.0/30 is subnetted, 1 subnets
O E1 192.168.1.0 [110/22] via 10.1.0.2, 00:03:58, FastEthernet0/0
[edit] R0 – show ip ospf database example – OSPF Distribute-list applied
The output below shows another type-5 LSA from R2 which generates the route. OSPF on R0 will add this LSA to it’s database because it must keep the database consistent.
R0#show ip ospf database

OSPF Router with ID (172.16.0.1) (Process ID 1)

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count
172.16.0.1 172.16.0.1 1135 0x80000004 0x008449 2
172.16.0.2 172.16.0.2 1197 0x80000002 0x00A4FB 3
172.16.0.3 172.16.0.3 270 0x80000006 0x00D6E8 2

Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum
10.1.0.1 172.16.0.1 1202 0x80000001 0x00E70F
10.2.0.2 172.16.0.3 1198 0x80000001 0x00D917

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag
192.168.1.0 172.16.0.3 262 0x80000001 0x00F009 0
[edit] EIGRP distribute-list configuration examples
[edit] Device Configurations
[edit] R0 (172.16.0.1)
router eigrp 1
network 10.1.0.0 0.0.0.3
network 172.16.0.1 0.0.0.0
auto-summary
!
[edit] R1 (172.16.0.2)
router eigrp 1
network 10.1.0.0 0.0.0.3
network 10.2.0.0 0.0.0.3
network 172.16.0.2 0.0.0.0
auto-summary
!
[edit] R2 (172.16.0.3)
router eigrp 1
redistribute connected
network 10.2.0.0 0.0.0.3
network 172.16.0.3 0.0.0.0
auto-summary
!
[edit] EIGRP - Default, standard routing (No distribute-list)
[edit] R1 – show ip route – EIGRP default standard routing
In the below example, we can see that the route from R2 makes it into EIGRP as an EIGRP external route. This is routing as usual and is expected.
R1#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
D 172.16.0.0/16 is a summary, 00:01:43, Null0
C 172.16.0.2/32 is directly connected, Loopback1
10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
C 10.2.0.0/30 is directly connected, FastEthernet1/0
D 10.0.0.0/8 is a summary, 00:02:07, Null0
C 10.1.0.0/30 is directly connected, FastEthernet0/0
192.168.1.0/30 is subnetted, 1 subnets
D EX 192.168.1.0 [170/156160] via 10.2.0.2, 00:01:31, FastEthernet1/0
[edit] R1 – show ip eigrp topology – EIGRP standard routing
This route is added into the EIGRP topology table with the below metrics, as expected.
R1#sh ip eigrp topology
IP-EIGRP Topology Table for AS(1)/ID(172.16.0.2)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status

P 10.2.0.0/30, 1 successors, FD is 28160
via Connected, FastEthernet1/0
P 10.0.0.0/8, 1 successors, FD is 28160
via Summary (28160/0), Null0
P 10.1.0.0/30, 1 successors, FD is 28160
via Connected, FastEthernet0/0
P 192.168.1.0/30, 1 successors, FD is 156160
via 10.2.0.2 (156160/128256), FastEthernet1/0
P 172.16.0.0/16, 1 successors, FD is 128256
via Summary (128256/0), Null0
P 172.16.0.2/32, 1 successors, FD is 128256
via Connected, Loopback1
[edit] R0 - show ip route - EIGRP Standard Routing
The route makes it from R1 to R0, with a next-hop of R1. This is routing as expected.
R0#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
D 172.16.0.0/16 is a summary, 00:02:28, Null0
C 172.16.0.1/32 is directly connected, Loopback0
10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
D 10.2.0.0/30 [90/30720] via 10.1.0.2, 00:02:35, FastEthernet0/0
D 10.0.0.0/8 is a summary, 00:02:44, Null0
C 10.1.0.0/30 is directly connected, FastEthernet0/0
192.168.1.0/30 is subnetted, 1 subnets
D EX 192.168.1.0 [170/158720] via 10.1.0.2, 00:01:53, FastEthernet0/0
[edit] R0 – show ip eigrp topology – EIGRP standard routing
The EIGRP route also makes it into the EIGRP topology of router R0, as expected.
R0#sh ip eigrp topology
IP-EIGRP Topology Table for AS(1)/ID(172.16.0.1)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status

P 10.2.0.0/30, 1 successors, FD is 30720
via 10.1.0.2 (30720/28160), FastEthernet0/0
P 10.0.0.0/8, 1 successors, FD is 28160
via Summary (28160/0), Null0
P 10.1.0.0/30, 1 successors, FD is 28160
via Connected, FastEthernet0/0
P 192.168.1.0/30, 1 successors, FD is 158720
via 10.1.0.2 (158720/156160), FastEthernet0/0
P 172.16.0.0/16, 1 successors, FD is 128256
via Summary (128256/0), Null0
P 172.16.0.1/32, 1 successors, FD is 128256
via Connected, Loopback0
[edit] EIGRP Distribution list configuration
In the below example, a distribute-list is applied to an interface using EIGRP. In EIGRP, a distribute-list will block route entries from entering the topology table. OSPF and EIGRP maintain their routing tables and make routing decisions differently. OSPF has a single database for the entire network, and each router has the same view of the network. EIGRP maintains a single view for each router. EIGRP operates in a ‘routing by rumor’ method, in which it only learns routes that it’s direct neighbors tell it. This is why it is referred to as a ‘hybrid’ routing protocol, in that it routes by rumors yet still supports link state advertisements and trigged updates.
[edit] R0 Config (172.16.0.3)
router eigrp 1
network 10.1.0.0 0.0.0.3
network 10.2.0.0 0.0.0.3
network 172.16.0.2 0.0.0.0
distribute-list 50 in FastEthernet1/0
auto-summary
!
access-list 50 deny 192.168.1.0 0.0.0.255
access-list 50 permit any
!
[edit] R1 – show ip route – EIGRP Distribute-list applied
R1 does not have 192.168.1.0/24 in it’s routing table anymore since we removed it from the running configuration. We can also see that there’s an EIGRP adjacency change when we apply the configuration, showing that it is truly a routing-by-rumor hybrid protocol and the neighbors topology has changed.
*Mar 1 03:11:13.651: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 10.2.0.2 (FastEthernet1/0) is resync: route configuration changed

R1#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
D 172.16.0.0/16 is a summary, 00:07:56, Null0
C 172.16.0.2/32 is directly connected, Loopback1
10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
C 10.2.0.0/30 is directly connected, FastEthernet1/0
D 10.0.0.0/8 is a summary, 00:08:20, Null0
C 10.1.0.0/30 is directly connected, FastEthernet0/0
**** 192.168.1.0/24 is NOT HERE as per distribute-list ****
[edit] R1 – Show ip eigrp topology – EIGRP distribute-list applied
Unsurprisingly, the distribute-list command has rejected the EIGRP route advertised from R2 and it does not make it into the EIGRP topology table.
R1#sh ip eigrp topology
IP-EIGRP Topology Table for AS(1)/ID(172.16.0.2)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status

P 10.2.0.0/30, 1 successors, FD is 28160
via Connected, FastEthernet1/0
P 10.0.0.0/8, 1 successors, FD is 28160
via Summary (28160/0), Null0
P 10.1.0.0/30, 1 successors, FD is 28160
via Connected, FastEthernet0/0
P 172.16.0.0/16, 1 successors, FD is 128256
via Summary (128256/0), Null0
P 172.16.0.2/32, 1 successors, FD is 128256
via Connected, Loopback1
[edit] R0 – show ip route – EIGRP distribute-list applied
When we get to R0, we can see that 192.168.1.0/24 is also not here --- Since EIGRP routes by rumor and not by a shared topology view, it has no idea that 192.168.1.0/24 is connected to R1, since R1 has rejected the route and topology entry with a distribute-list. This is the biggest difference between OSPF and EIGRP – Distribute-lists on EIGRP do exactly what they are intended to do, while OSPF will not give results.
R0#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
D 172.16.0.0/16 is a summary, 00:08:23, Null0
C 172.16.0.1/32 is directly connected, Loopback0
10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
D 10.2.0.0/30 [90/30720] via 10.1.0.2, 00:08:29, FastEthernet0/0
D 10.0.0.0/8 is a summary, 00:08:38, Null0
C 10.1.0.0/30 is directly connected, FastEthernet0/0
[edit] R0 – show ip eigrp topology – EIGRP distribute-list applied
As mentioned prior, EIGRP does not have a topology entry for 192.168.1.0/24 – R0 never hears about the topology entry, since R1 rejects it outright.
R0#sh ip eigrp topology
IP-EIGRP Topology Table for AS(1)/ID(172.16.0.1)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status

P 10.2.0.0/30, 1 successors, FD is 30720
via 10.1.0.2 (30720/28160), FastEthernet0/0
P 10.0.0.0/8, 1 successors, FD is 28160
via Summary (28160/0), Null0
P 10.1.0.0/30, 1 successors, FD is 28160
via Connected, FastEthernet0/0
P 172.16.0.0/16, 1 successors, FD is 128256
via Summary (128256/0), Null0
P 172.16.0.1/32, 1 successors, FD is 128256
via Connected, Loopback0
[edit] Conclusion
In the examples listed above, we can display the routing protocol differences between EIGRP and OSPF when distribute-lists are used. OSPF distribute lists only change routing decisions on which routes from the OSPF database to add to the RIB and FIB (Forwarding and Routing information bases), or the routing table, on the specific router, but continues to advertise LSAs to other OSPF routers. EIGRP distribute-lists reject the topology and routes advertised from neighbors due to it’s route-by-rumor design, and as such, those routes are not advertised to any other EIGRP neighbors.
References: Cisco IOS 12.4(18), IP Plus on Cisco 3640 series chassis. GNS3, version 0.4 https://gns3.net, based on open-source Dynagen and Dynamips.
i,
Can anyone help me understand prefix lists a little better ?
As can be seen from the output below, I have tried to configure a distribute list within eigrp with the aim of filtering just the route 172.16.1.0/24 .

Using > ip prefix-list test seq 5 deny 172.16.1.0/24

router eigrp 1
network 10.0.24.0 0.0.7.255
network 172.16.0.0
distribute-list prefix test out
no auto-summary

However when I go to R2 the list has filtered all routes 172.16.1.0, 172.16.2.0, 172.16.3.0,172.16.4.0 etc

Is it not possible to filter just one route within a classful network with a prefix list or am I missing something ?

Thanks in advance. Phil.

full router config below :

R2#show run
Building configuration...
Current configuration : 1850 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R2
!
boot-start-marker
boot-end-marker
!
enable password cisco
!
no aaa new-model
no network-clock-participate slot 1
no network-clock-participate wic 0
ip cef
!
!
!
!
no ip domain lookup
ip host r1 10.0.24.1
ip host sw1 10.0.24.3
!
multilink bundle-name authenticated
!
!
!
!
!
username phil
archive
log config
hidekeys
!
!
!
!
!
!
!
interface Loopback1
ip address 172.16.1.2 255.255.255.0
!
interface Loopback2
ip address 172.16.2.2 255.255.255.0
!
interface Loopback3
ip address 172.16.3.2 255.255.255.0
!
interface Loopback4
ip address 172.16.4.2 255.255.255.0
!
interface Loopback5
ip address 172.16.5.2 255.255.255.0
!
interface Loopback6
ip address 172.16.6.2 255.255.255.0
!
interface Loopback7
ip address 172.16.7.2 255.255.255.0
!
interface Loopback8
ip address 172.16.8.2 255.255.255.0
!
interface Loopback9
ip address 172.16.9.2 255.255.255.0
!
interface Loopback10
ip address 172.16.10.2 255.255.255.0
!
interface Loopback11
ip address 172.16.11.2 255.255.255.0
!
interface Loopback12
ip address 172.16.12.2 255.255.255.0
!
interface Loopback13
no ip address
!
interface Loopback14
no ip address
!
interface Loopback15
no ip address
!
interface FastEthernet0/0
ip address 10.0.24.2 255.255.255.248
duplex auto
speed auto
!
interface Serial0/0
no ip address
no fair-queue
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
router eigrp 1
network 10.0.24.0 0.0.7.255
network 172.16.0.0
distribute-list prefix test out
no auto-summary
!
ip forward-protocol nd
!
!
ip http server
no ip http secure-server
!
!
ip prefix-list test seq 5 deny 172.16.1.0/24
!
!
!
!
control-plane
!
!
!
line con 0
line aux 0
line vty 0 4
password cisco
login
!
!
end
R2#

Prefix list in EIGRP redistribution
Zone:
Network Routers
Right now, R1 prefers R3 for everything. I would like to change this, so R1 prefers R2 for 172.16.1.1. But goes through R3 for everything else. Can this be done with a prefix list on R2 only?

ie, config to add to R2:

ip prefix-list mylist seq 5 permit 172.16.1.1/32
access-list 1 permit any
!
route-map mymap permit 10
match ip address prefix-list mylist
set metric 100000 100 255 1 1500
!
route-map mymap permit 20
match ip address 1
set metric 10 100 255 1 1500


labospfeigrp.jpg (109 KB) (File Type Details)
b

EIGRP Support for Route Map Filtering

EIGRP Support for Route Map Filtering
________________________________________
First Published: May 17, 2004
Last Updated: September 28, 2007
The EIGRP Support for Route Map Filtering feature enables Enhanced Interior Gateway Routing Protocol (EIGRP) to interoperate with other protocols by filtering inbound and outbound traffic based on complex route map options. In addition to the existing route map facility, several extended filtering options are introduced to provide EIGRP-specific match choices.
Finding Feature Information in This Module
Your Cisco IOS software release may not support all of the features documented in this module. To reach links to specific feature documentation in this module and to see a list of the releases in which each feature is supported, use the "Feature Information for EIGRP Support for Route Map Filtering" section.
Finding Support Information for Platforms and Cisco IOS and Catalyst OS Software Images
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
• Information About EIGRP Support for Route Map Filtering
• How to Configure EIGRP Support for Route Map Filtering
• Configuration Examples for EIGRP Support for Route Map Filtering
• Additional References
• Command Reference
• Feature Information for EIGRP Support for Route Map Filtering
Information About EIGRP Support for Route Map Filtering
To implement EIGRP route map filtering, you should understand the following concept:
• EIGRP Route Map Support
EIGRP Route Map Support
EIGRP support for route map filtering enables EIGRP to interoperate with other protocols by filtering inbound and outbound traffic based on route map options. Additional EIGRP-specific match choices are introduced to allow flexibility in fine-tuning EIGRP network operations.
EIGRP now supports the route map filtering capability that exists for other routing protocols to filter routes being redistributed into their protocol. For more details about understanding and configuring route maps, see the Enabling Policy Routing section of the "Configuring IP Routing Protocol-Independent Features" chapter of the Cisco IOS IP Routing Protocols Configuration Guide, Release 12.4T.
New match options allow EIGRP to filter internal and external routes based on source protocols, to match a metric against a range, and to match on an external protocol metric.
EIGRP can be configured to filter traffic using a route map and the redistribute or distribute-list commands. Using a route map with the redistribute command allows routes that are redistributed from the routing table to be filtered with a route map before being admitted into an EIGRP topology table. Routes that are dynamically received from, or advertised to, EIGRP peers can be filtered by adding a route map option to the distribute-list command.
A route map may be configured with both the redistribute and the distribute-list commands in the same routing process. When a route map is used with a distribute-list command that is configured for inbound or outbound filtering, route packets that are learned from or advertised to EIGRP peers can be processed with the route map to provide better control of route selection during the route exchange process. Redistribution serves as a mechanism to import routes into the EIGRP topology table from a routing table. A route map configured with the redistribute command adds flexibility to the redistribution capability and results in a more specific redistributed route selection.
In summary, demands for EIGRP to interoperate with other protocols and flexibility in fine-tuning network operation necessitate the capability to filter traffic using a route map.
How to Configure EIGRP Support for Route Map Filtering
This section contains the following tasks:
• Configuring EIGRP Metrics Using a Route Map (required)
• Verifying EIGRP Metrics (optional)
Configuring EIGRP Metrics Using a Route Map
Perform this task configure EIGRP metrics using a route map. In the Detailed Steps below, the EIGRP metrics used for filtering are configured within a route map. The first match clause defines EIGRP routes that contain an external protocol metric between 400 and 600 inclusive;the second match clause defines EIGRP external routes that match a source protocol of BGP and the autonomous system 45000. When the two match clauses are true, a tag value of the destination routing protocol is set to 5. This route map can be used with the distribute-list command, see the "Configuring EIGRP Metrics Using a Route Map: Examples" section for an example configuration.
SUMMARY STEPS
1. enable
2. configure terminal
3. route-map map-tag [permit | deny] [sequence-number]
4. match metric {metric-value | external metric-value} [+- deviation-number]
5. match source-protocol source-protocol [autonomous-system-number]
6. set tag source-protocol [autonomous-system-number]
7. exit
8. router eigrp as-number
9. network ip-address
10. distribute-list route-map map-tag in
DETAILED STEPS
Command or Action Purpose
Step 1 enable
Example:
Router> enable Enables privileged EXEC mode.
• Enter your password if prompted.

Step 2 configure terminal
Example:
Router# configure terminal Enters global configuration mode.
Step 3 route-map map-tag [permit | deny] [sequence-number]
Example:
Router(config)# route-map metric_range Enters route-map configuration mode.
Step 4 match metric {metric-value | external metric-value} [+- deviation-number]
Example:
Router(config-route-map)# match metric external 500 +- 100 Specifies a match clause that redistributes EIGRP routes that match an internal or external protocol metric.
• metric-value—Internal protocol metric, which can be an EIGRP five-part metric. The range is from 1 to 4294967295.
• external—External protocol metric. The range is from 1 to 4294967295.
• +- deviation-number—(Optional) Represents a standard deviation. The deviation can be any number. There is no default.
• In this example, EIGRP routes that contain an external protocol metric between 400 and 600 inclusive are redistributed.
Note When you specify a metric deviation with the + and - keywords, the router will match any metric that falls inclusively in that range.
Note The external protocol metric is not the same as the EIGRP assigned route metric which is a figure computed from EIGRP vectorized metric components (delay, bandwidth, reliability, load, and MTU).
Step 5 match source-protocol source-protocol [autonomous-system-number]
Example:
Router(config-route-map)# match source-protocol bgp 45000 Specifies a match clause that redistributes EIGRP external routes that match a source protocol.
• source-protocol—Protocol to match. The valid keywords are bgp, connected, eigrp, isis, ospf, rip, and static. There is no default.
• autonomous-system-number—(Optional) Autonomous system number. The autonomous-system-number argument is not applicable to the connected, static, and rip keywords. The range is from 1 to 65535. There is no default.
• In this example, EIGRP external routes that match a source protocol of BGP and the autonomous system 45000.
Step 6 set tag tag-value
Example:
Router(config-route-map)# set tag 5 Sets a tag value of the destination routing protocol when all the match criteria of a route map are met.
• In this example, the tag value of the destination routing protocol is set to 5.
Step 7 exit
Example:
Router(config-route-map)# exit Exits configuration mode to the next highest mode in the CLI mode hierarchy.
Step 8 router eigrp as-number
Example:
Router(config)# router eigrp 1 Configures the EIGRP routing process.
Step 9 network ip-address
Example:
Router(config-router)# network 172.16.0.0 Specifies a network for the EIGRP routing process.
Step 10 distribute-list route-map map-tag in
Example:
Router(config)# distribute-list route-map metric_range in Filters networks received in updates.
• This example uses a route map to filter the networks. The route map named "metric_range" was identifed in Step 3 above.
Verifying EIGRP Metrics
To verify that both the EIGRP metric and the external protocol metrics have been configured, perform the following step.
SUMMARY STEPS
1. enable
2. show ip eigrp topology [autonomous-system-number | ip-address [mask]] [active | all-links | detail-links | pending | summary | zero-successors]
DETAILED STEPS
________________________________________
Step 1 enable
Enables privileged EXEC mode. Enter your password if prompted.
Router# enable

Step 2 show ip eigrp topology [autonomous-system-number | ip-address [mask]] [active | all-links | detail-links | pending | summary | zero-successors]
Use this command to display the internal EIGRP metrics for a specified IP address, for example:
Router# show ip eigrp topology 172.16.1.0/24

IP-EIGRP (AS 45000): Topology entry for 172.16.1.0/24
State is Passive, Query origin flag is 1, 1 Successor(s), FD is 2169856
Routing Descriptor Blocks:
0.0.0.0 (Serial4/0), from Connected, Send flag is 0x0
Composite metric is (2169856/0), Route is Internal
Vector metric:
Minimum bandwidth is 1544 Kbit
Total delay is 20000 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 0

In the following example, the external EIGRP metrics for a specified IP address are displayed:
Router# show ip eigrp topology 192.168.1.0/24

IP-EIGRP (AS 45000): Topology entry for 192.168.1.0/24
State is Passive, Query origin flag is 1, 1 Successor(s), FD is 2169856
Routing Descriptor Blocks:
0.0.0.0 (Serial4/0), from Connected, Send flag is 0x0
Composite metric is (2169856/0), Route is External
Vector metric:
Minimum bandwidth is 1544 Kbit
Total delay is 20000 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 1
External data:
Originating router is 10.89.245.1
AS number of route is 0
External protocol is Connected, external metric is 0
Administrator tag is 0 (0x00000000)
________________________________________
Configuration Examples for EIGRP Support for Route Map Filtering
This section contains the following configuration example:
• Configuring EIGRP Metrics Using a Route Map: Examples
Configuring EIGRP Metrics Using a Route Map: Examples
The following example shows how to configure a route map to match an EIGRP external protocol metric route with an allowable deviation of 100, a source protocol of BGP, and an autonomous system 45000. When the two match clauses are true, the tag value of the destination routing protocol is set to 5. The route map is used to distribute incoming packets for an EIGRP process.
route-map metric_range
match metric external 500 +- 100
match source-protocol bgp 45000
set tag 5
!
router eigrp 1
network 172.16.0.0
distribute-list route-map metric_range in

The following example shows how to configure a route map to match EIGRP routes with a metric of 110, 200, or an inclusive range of 700 to 800. When the match clause is true, the tag value of the destination routing protocol is set to 10. The route map is used to redistribute EIGRP packets.
route-map metric_eigrp
match metric 110 200 750 +- 50
set tag 10
!
router eigrp 1
network 172.21.1.0/24
redistribute eigrp route-map metric_eigrp
Additional References
The following sections provide references related to the EIGRP Support for Route Map Filtering feature.
Related Documents
Related Topic Document Title
IP routing protocols overview and configuration Cisco IOS IP Configuration Guide, Part 2: IP Routing Protocols, Release 12.3
IP routing commands including syntax, usage guidelines, and examples • Cisco IOS IP Command Reference, Volume 2 of 4: Routing Protocols, Release 12.3T
• Cisco IOS IP Routing Protocols Command Reference, Release 12.2SR
• Cisco IOS IP Routing Protocols Command Reference, Release 12.2SX


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Command Reference
This section documents only commands that are new or modified.
• match metric (IP)
• match source-protocol
• show ip eigrp topology
match metric (IP)
To redistribute routes with the specified metric, use the match metric command in route-map configuration mode. To remove the entry for the redistributed route from the routing table, use the no form of this command.
match metric {metric-value | external metric-value} [+- deviation-number]
no match metric {metric-value | external metric-value} [+- deviation-number]
Syntax Description
metric-value Internal route metric, which can be an Enhanced Interior Gateway Routing Protocol (EIGRP) five-part metric. The range is from 1 to 4294967295.
external External protocol associated with a route and interpreted by a source protocol.
+- deviation-number (Optional) A standard deviation number that will offset the number configured for the metric-value argument. The deviation-number argument can be any number. There is no default.
Note When you specify a deviation of the metric with the + and - keywords, the router will match any metric that falls inclusively in that range.

Command Default
No filtering is performed on a metric value.
Command Modes
Route-map configuration
Command History
Release Modification
11.2 This command was introduced.
12.3(8)T The external and +- keywords and deviation-number argument were added.
12.2(33)SRA This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(33)SXH This command was integrated into Cisco IOS Release 12.2(33)SXH.

Usage Guidelines
Use the route-map global configuration command and the match and set route-map configuration commands to define the conditions for redistributing routes from one routing protocol into another. Each route-map command has a list of match and set commands associated with it. The match commands specify the match criteria—the conditions under which redistribution is allowed for the current route-map command. The set commands specify the set actions—the particular redistribution actions to perform if the criteria enforced by the match commands are met. The no route-map command deletes the route map.
The match route-map configuration command has multiple formats. The match commands can be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
A route map can have several parts. Any route that does not match at least one match clause relating to a route-map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want to modify only some data, you must configure a second route map section with an explicit match specified.

________________________________________
Note An external protocol route metric is not the same as the EIGRP assigned route metric which is a figure computed using EIGRP vectorized metric components (delay, bandwidth, reliability, load, and MTU).
________________________________________
Examples
In the following example, routes with the metric 5 will be redistributed:
route-map name
match metric 5

In the following example, any metric that falls inclusively in the range from 400 to 600 is matched:
route-map name
match metric 500 +- 100

The following example shows how to configure a route map to match an EIGRP external protocol metric route with an allowable deviation of 100, a source protocol of BGP, and an autonomous system 45000. When the two match clauses are true, the tag value of the destination routing protocol is set to 5. The route map is used to distribute incoming packets for an EIGRP process.
route-map metric_range
match metric external 500 +- 100
match source-protocol bgp 45000
set tag 5
!
router eigrp 45000
network 172.16.0.0
distribute-list route-map metric_range in
Related Commands
Command Description
match as-path Matches a BGP autonomous system path access list.
match community Matches a BGP community.
match interface (IP) Distributes any routes that have their next hop out one of the interfaces specified.
match ip address Distributes any routes that have a destination network number address that is permitted by a standard or extended access list, and performs policy routing on packets.
match ip next-hop Redistributes any routes that have a next hop router address passed by one of the access lists specified.
match ip route-source Redistributes routes that have been advertised by routers and access servers at the address specified by the access lists.
match route-type (IP) Redistributes routes of the specified type.
match tag Redistributes routes in the routing table that match the specified tags.
route-map (IP) Defines the conditions for redistributing routes from one routing protocol into another, or enables policy routing.
set as-path Modifies an autonomous system path for BGP routes.
set automatic-tag Automatically computes the tag value.
set community Sets the BGP communities attribute.
set level (IP) Indicates where to import routes.
set local-preference Specifies a preference value for the autonomous system path.
set metric (BGP, OSPF, RIP) Sets the metric value for a routing protocol.
set metric-type Sets the metric type for the destination routing protocol.
set next-hop Specifies the address of the next hop.
set tag (IP) Sets a tag value of the destination routing protocol.

match source-protocol
To match Enhanced Interior Gateway Routing Protocol (EIGRP) external routes based on a source protocol and autonomous system number, use the match source-protocol command in route-map configuration mode. To remove the protocol to be matched, use the no form of this command.
match source-protocol source-protocol [autonomous-system-number]
no match source-protocol source-protocol [autonomous-system-number]
Syntax Description
source-protocol Protocol to match. The valid keywords are bgp, connected, eigrp, isis, ospf, rip, and static. There is no default.
autonomous-system-number (Optional) Autonomous system number. This argument is not applicable to the connected, static, and rip keywords. The range is from 1 to 65535. There is no default.

Command Default
EIGRP external routes are not matched on a source protocol and autonomous system number.
Command Modes
Route-map configuration
Command History
Release Modification
12.3(8)T This command was introduced.
12.2(33)SRA This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(33)SXH This command was integrated into Cisco IOS Release 12.2(33)SXH.

Usage Guidelines
This command may not be useful with a redistribution operation that employs route maps because redistribution usually requires the configuration of a source protocol and an autonomous system value in order to redistribute. In many cases, it is more useful to configure a route map that includes matching the route type based on the source protocol and autonomous system using the distribute-list command for EIGRP.
Examples
The following example shows how to configure a route map to match a source protocol of BGP and an autonomous system 45000. When the match clause is true, the tag value of the destination routing protocol is set to 5. The route map is used to distribute incoming packets for an EIGRP process.
route-map metric_source
match source-protocol bgp 45000
set tag 5
!
router eigrp 45000
network 172.16.0.0
distribute-list route-map metric_source in
Related Commands
Command Description
distribute-list Filters networks received in updates.
match as-path Matches a BGP autonomous system path access list.
match community Matches a BGP community.
match interface (IP) Distributes any routes that have their next hop out one of the interfaces specified.
match ip address Distributes any routes that have a destination network number address that is permitted by a standard or extended access list, and performs policy routing on packets.
match ip next-hop Redistributes any routes that have a next hop router address passed by one of the access lists specified.
match ip route-source Redistributes routes that have been advertised by routers and access servers at the address specified by the access lists.
match route-type (IP) Redistributes routes of the specified type.
match tag Redistributes routes in the routing table that match the specified tags.
route-map (IP) Defines the conditions for redistributing routes from one routing protocol into another, or enables policy routing.
set as-path Modifies an autonomous system path for BGP routes.
set automatic-tag Automatically computes the tag value.
set community Sets the BGP communities attribute.
set level (IP) Indicates where to import routes.
set local-preference Specifies a preference value for the autonomous system path.
set metric (BGP, OSPF, RIP) Sets the metric value for a routing protocol.
set metric-type Sets the metric type for the destination routing protocol.
set next-hop Specifies the address of the next hop.
set tag (IP) Sets a tag value of the destination routing protocol.
set weight Specifies the BGP weight for the routing table.

show ip eigrp topology
To display entries in the Enhanced Interior Gateway Routing Protocol (EIGRP) topology table, use the show ip eigrp topology command in privileged EXEC mode.
show ip eigrp topology [autonomous-system-number | ip-address [mask] | name [interfaces]] [active | all-links | pending | summary | zero-successors]
Syntax Description
autonomous-system-number (Optional) Autonomous system number.
ip-address (Optional) IP address. When specified with a mask, a detailed description of the entry is provided.
mask (Optional) Subnet mask. The mask is entered as a slash mark followed by the prefix length.
name (Optional) EIGRP-IPv4 topology table name. This name is the topology identifier and shows the topology-related information for Multi-Topology Routing (MTR).
interfaces (Optional) Displays information about interfaces, on which EIGRP is configured, in a topology.
active (Optional) Displays only active entries in the EIGRP topology table.
all-links (Optional) Displays all entries in the EIGRP topology table.
pending (Optional) Displays all entries in the EIGRP topology table that are waiting for an update from a neighbor or are waiting to reply to a neighbor.
summary (Optional) Displays a summary of the EIGRP topology table.
zero-successors (Optional) Displays available routes in the EIGRP topology table.

Command Default
If this command is used without any keywords or arguments, then only routes that are feasible successors are displayed.
Command Modes
Privileged EXEC
Command History
Release Modification
10.0 This command was introduced.
12.3(8)T This command was enhanced to display internal and external EIGRP routes.
12.2(33)SRA This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(33)SRB The name argument and interfaces keyword were added to support MTR.
12.2(33)SXH This command was integrated into Cisco IOS Release 12.2(33)SXH.

Usage Guidelines
The show ip eigrp topology command can be used without any keywords or arguments. If this command is used without any keywords or arguments, then only routes that are feasible successors are displayed. The show ip eigrp topology command can be used to determine Diffusing Update Algorithm (DUAL) states and to debug possible DUAL problems. The show ip eigrp topology name command option indicates that the output displayed will be for a named service topology for MTR.
Examples
The following is sample output from the show ip eigrp topology command:
Router# show ip eigrp topology

IP-EIGRP Topology Table for process 77

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - Reply status

P 10.16.90.0 255.255.255.0, 2 successors, FD is 0
via 10.16.80.28 (46251776/46226176), Ethernet0
via 10.16.81.28 (46251776/46226176), Ethernet1
via 10.16.80.31 (46277376/46251776), Serial0
P 10.16.81.0 255.255.255.0, 1 successors, FD is 307200
via Connected, Ethernet1
via 10.16.81.28 (307200/281600), Ethernet1
via 10.16.80.28 (307200/281600), Ethernet0
via 10.16.80.31 (332800/307200), Serial0

In the following examples, EIGRP metrics for specified internal and external routes are displayed:
Router# show ip eigrp topology 10.2.1.0/24

IP-EIGRP (AS 1): Topology entry for 10.2.1.0/24

State is Passive, Query origin flag is 1, 1 Successor(s), FD is 281600 Routing Descriptor
Blocks:
0.0.0.0 (Ethernet0/0), from Connected, Send flag is 0x0 Composite metric is (281600/0),
Route is Internal !This is the internal route.
Vector metric: Minimum bandwidth is 10000 Kbit
Total delay is 1000 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 0

Router# show ip eigrp topology 10.4.80.0/20

IP-EIGRP (AS 1): Topology entry for 10.4.80.0/20

State is Passive, Query origin flag is 1, 1 Successor(s), FD is 409600
Routing Descriptor Blocks:
10.2.1.1 (Ethernet0/0), from 10.2.1.1, Send flag is 0x0
Composite metric is (409600/128256), Route is External !This is the external route.
Vector metric:
Minimum bandwidth is 10000 Kbit
Total delay is 6000 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 1
External data:
Originating router is 10.89.245.1
AS number of route is 0
External protocol is Connected, external metric is 0
Administrator tag is 0 (0x00000000)

Table 1 describes the significant fields shown in the displays.
Table 1 show ip eigrp topology Field Descriptions
Field Description
Codes State of this topology table entry. Passive and Active refer to the EIGRP state with respect to this destination; Update, Query, and Reply refer to the type of packet that is being sent.
P - Passive No EIGRP computations are being performed for this destination.
A - Active EIGRP computations are being performed for this destination.
U - Update Indicates that an update packet was sent to this destination.
Q - Query Indicates that a query packet was sent to this destination.
R - Reply Indicates that a reply packet was sent to this destination.
r - Reply status Flag that is set after the software has sent a query and is waiting for a reply.
10.16.90.0 Destination IP network number.
255.255.255.0 Destination subnet mask.
successors Number of successors. This number corresponds to the number of next hops in the IP routing table. If "successors" is capitalized, then the route or next hop is in a transition state.
FD Feasible distance. The feasible distance is the best metric to reach the destination or the best metric that was known when the route went active. This value is used in the feasibility condition check. If the reported distance of the router (the metric after the slash) is less than the feasible distance, the feasibility condition is met and that path is a feasible successor. Once the software determines it has a feasible successor, it need not send a query for that destination.
via IP address of the peer that told the software about this destination. The first n of these entries, where n is the number of successors, is the current successors. The remaining entries on the list are feasible successors.
(46251776/46226176) The first number is the EIGRP metric that represents the cost to the destination. The second number is the EIGRP metric that this peer advertised.
Ethernet0 Interface from which this information was learned.
Serial0 Interface from which this information was learned.

Feature Information for EIGRP Support for Route Map Filtering
Table 2 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

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Note Table 2 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.
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Table 2 Feature Information for EIGRP Support for Route Map Filtering
Feature Name Releases Feature Information
EIGRP Support for Route Map Filtering 12.2(33)SRA
12.2(33)SXH
12.3(8)T The EIGRP Support for Route Map Filtering feature enables EIGRP to interoperate with other protocols by filtering inbound and outbound traffic based on complex route map options. In addition to the existing route map facility, several extended filtering options are introduced to provide EIGRP-specific match choices.
The following commands were introduced or modified by this feature: match metric (IP), match source-protocol, show ip eigrp topology.