03-11-2011 01:52 AM - edited 03-04-2019 11:43 AM
Hi,
We have a MPLS network to interconnect our remote offices with our datacenters.
On the remote offices we use C1841 routers with ios c1841-broadband-mz.124-25d.bin.
The lan interface is a dot1q trunk with 3 subinterfaces (and so 3 subnets)
Recently we ran in to routing issues on 2 routers:
We use RIPv2 as routing protocol and redistribute the connected lan subnets.
(we keep a full routing table - no filtering).
When we have the problem, 1 or 2 LAN subnets are no longer advertised via RIP (although the subinterfaces stay up/up).
The other subnet is still advertised.
We have a routing table/rip database with around 260 routes.
To overcome the issue, we configured an inbound distribute-list to only accept the default route and some specific subnets.
Since then the issue is solved, but I would like to know if it is a limitation on the router or something else.
I've also done RIP debugging, but nothing exciting was shown...
herewith the config:
interface FastEthernet0/0
bandwidth 100000
no ip address
speed 100
full-duplex
!
interface FastEthernet0/0.11
encapsulation dot1Q 11 native
ip address 10.72.52.1 255.255.254.0
ip helper-address 10.72.10.51
ip helper-address 10.72.16.51
ip directed-broadcast
!
interface FastEthernet0/0.21
encapsulation dot1Q 21
ip address 10.73.52.1 255.255.254.0
ip helper-address 10.72.10.51
ip helper-address 10.72.16.51
ip directed-broadcast
!
int FA0/0.31
encapsulation dot1Q 31
ip address 10.73.54.1 255.255.254.0
!
router rip
version 2
redistribute connected
network 192.168.100.0
no auto-summary
!
Thanks,
tom
03-14-2011 11:40 PM
Hi Tom,
So the only change you made is an inbound filter to permit a default and a few more.
It could be split horizon where a few of the local connected subnets were learned on the interface accidentally and hence these were not advertised out, even though the subinterfaces were up. Just a possible theory.
sh ip rip database when the problem occured would help to further dig down.
Regards,
Mani
03-25-2011 02:18 AM
Hi Mani,
Very strange, i've put the explicit 'ip split-horizon' command on the ATM0/0/0.1 interface and removed the inbound distributelist.
Since 2 days no issues ...
The thing is that i've never configured the 'no ip split-horizon' command somewhere ...
Thanks
tom
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