Prefix list not working as it should ... help!

[steven.crutchley]

I am attempting to apply a prefix list to filter EIGRP routes (via a distribute-list) but it is not working.

R2 is connected to R4 via point-to-point frame relay on DLCI 204 (frame-relay map is up and they are EIGRP neighbours). R4 has 192.168.4.0/24 as a LAN and is advertsing it to R2 (connected via DLCI 402).

R2 (sub) interface has IP 192.168.24.1

R4 interface has IP 192.168.24.2

My goal is to filter any route for 192.168.4.0/24 that R4 sends to R2. This will force R2 to learn about a route to 192.168.4.0/24 via 10.4.4.1 (this is R1 - a router also connected to R4). But the prefix list, despite being applied to the distribution list is not working. My setup is as follows:

R2#show ip prefix-list
ip prefix-list block4: 2 entries
   seq 5 deny 192.168.4.0/24
   seq 10 permit 0.0.0.0/0 le 32
R2#show run | s router
router eigrp 12
network 10.2.2.0 0.0.0.3
network 10.4.4.0 0.0.0.3
network 172.16.23.0 0.0.0.255
network 172.16.24.0 0.0.0.255
distribute-list block4 in Serial0/0.204
no auto-summary
R2#show ip int br
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            10.2.2.1        YES NVRAM  up                    up
Serial0/0                  unassigned      YES NVRAM  up                    up
Serial0/0.203              172.16.23.1     YES NVRAM  up                    up
Serial0/0.204              172.16.24.1     YES NVRAM  up                    up
FastEthernet0/1            10.4.4.2        YES NVRAM  up                    up
Serial0/1                  unassigned      YES NVRAM  administratively down down
R2#show ip route 192.168.4.0
Routing entry for 192.168.4.0/24
  Known via "eigrp 12", distance 90, metric 2195456, type internal
  Redistributing via eigrp 12
  Last update from 172.16.24.2 on Serial0/0.204, 00:05:29 ago
  Routing Descriptor Blocks:
  * 172.16.24.2, from 172.16.24.2, 00:05:29 ago, via Serial0/0.204
      Route metric is 2195456, traffic share count is 1
      Total delay is 21000 microseconds, minimum bandwidth is 1544 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 1

R2#

As you can see, despite the application of the distribution list, R2 is still getting the route for 192.168.4.0/24 from R4...

This working using a standard ACL.

I can post a full network diagram if you wish but hopefully this should be enough information. Can anyone help?

[smehrnia · Accepted solution]

Hello steven,

u have a tiny little problem! unlike using ACLs, you have to use a keyword for utilizing prefix-lists with distribute-list.

distribute-list PREFIX block4 in s0/0.204

Hope it Helps,

plz Rate helpful posts,

Soroush.

[steven.crutchley]

Perfect!

Thank you so much. I've been going crazy over this one for a while.

It must have been looking for ACL named block4 without the prefix word in place.

Much obliged.