01-26-2009 04:18 AM - edited 03-04-2019 12:58 AM
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
01-26-2009 04:22 AM
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
01-26-2009 08:53 AM
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
01-26-2009 09:04 AM
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
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide