ospf route distribution

Unanswered Question
Jan 26th, 2009

we have the below network

isprouter1------switch 1------cus-router1

isprouter2----switch2---cus-router2

switch 1 and switch 2 are interconnected

cus-router1 one ethernet interface is connected to LAN siwtch 1 and cus-router2 one ethernet interface is connected to LAN switch 2

both these lan switches are interconnected and redistribute some static routes. those routes are learnt by both ISP routers. now when we removed the fast ehthernet interfce of cus-router 1 facing LAN switch, and tested the connection from a remote site to reach a network residributed via static from lan switches. a loop has occured. the packet is reaching isp router 2 and then goes to isp router 1 and forms a loop.

how do avoid this?

what can be done within ospf to avoid this and have a failover working. if any interfaces of any router fails, the redistributed routes should cause any loops

thanks

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Richard Burts Mon, 01/26/2009 - 04:22

Munaf

I wonder if the switches continue to redistribute some static routes even when the interface on cus-router1 is removed? It might help us figure out the problem if you could provide some configuration details from the switches and the customer routers.

HTH

Rick

followurself Mon, 01/26/2009 - 08:53

thnx for the reply

just to simply more, below is the diag

Isprter1 ---swtch a--cust-rter1--lanswitcha

| |

isprter2--swtch b--cust-rter2-lanswitchb

isprter1 and 2 are connected and so is lanswitcha and b

currently connection from cust-rter1 to lanswitcha is down

lanswitch b is the DR

sh ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

172.104.23.2 1 FULL/DROTHER 00:00:38 191.1.20.71 Vlan2

172.104.23.50 1 FULL/BDR 00:00:39 191.1.20.65 Vlan2

172.104.23.2 1 FULL/BDR 00:00:38 172.104.23.2 Vlan999

Isprter2 neigbor

sh ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

145.233.101.165 1 FULL/BDR 00:00:33 10.10.1.6 FastEthernet1/0

172.104.23.51 1 FULL/DROTHER 00:00:39 10.10.1.1 FastEthernet1/0

192.168.239.116 1 FULL/DROTHER 00:00:38 10.10.1.2 FastEthernet1/0

172.104.23.2 1 FULL/DROTHER 00:00:36 191.1.20.71 FastEthernet0/0

172.104.23.5 1 FULL/DR 00:00:33 191.1.20.73 FastEthernet0/0

We want to reach a network 10.1.90 and we reach isprter then a loop. The loop is within isprter1 and 2, cust-rter1 and 2

Below is the ip ospf database for 10.1.90.0 on isprter 1

7200#sh ip route | include 10.1.90

O E2 10.1.90.0/24 [110/10] via 10.10.1.2, 01:43:42, FastEthernet1/0

7200#sh ip ospf da

7200#sh ip ospf database | in

mfl-lnd-bt-7200#sh ip ospf database | include 10.1.90.0

10.1.90.0 172.104.23.2 547 0x800000B5 0x000B4D 0

10.1.90.0 172.104.23.5 597 0x800000B4 0x00FA5B 0

10.1.90.0 192.168.239.116 203 0x8000002F 0x003546 106795

We are missing something very basic and important

Richard Burts Mon, 01/26/2009 - 09:04

Munaf

To give us better information to work from can you post the output of show ip interface brief and the output of show ip route from each of the routers and switches?

HTH

Rick

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