Secondary IP address limitation

[tigist_abe]

I have configured one of the cisco 2600 router ethernet port with two IP address. I connected this port to two WAN links and the connection works as long as the Pimary IP network is up. If the WAn link for the primary IP network fails, the secondary IP network cannot communicate with the other WAN link.

Can someone please help me solve the problem

[tigist_abe]

Rick,

I have attached the connectivity and the IP addresses of the WAN link devices are:

Link1 IP address 172.31.2.1/24

Link2 IP address 172.31.22.1/24

f0/1 primary IP address 172.31.2.2/24

f0/1 secondary IP address 172.31.22.2/24

*My problem is when Link1 is down due to so many reasons; LAN users cannot communicate with the head office.

My intention is to enable LAN users to be able to use both links to communicate with the head office and If WAN link fails LAN uses must be able to communicate with the head office.

Tigist

[Richard Burts]

Tigist

I have looked at the drawing and it is somewhat helpful. It would be even more helpful if it showed the connections on the remote side of the WAN.

But I believe that the drawing is sufficient to confirm my theory of the problem in my previous post. Running RIP on f0/1 with primary and secondary addresses will send RIP updates with a source address of the primary address. RIP updates going over Link2 will be received by a device with address 172.31.22.1 and have a source address of 172.31.2.2. I believe that these RIP updates will be rejected because of the mismatch of the source address. Is it possible to get the output of show ip route from the remote when Link1 is down? This would be the best analysis of the problem and I believe that it would show that there are no routes learned from your router. If that is a problem, then the output of show ip route with both links up might be helpful. I suspect that if it was working as you want there would be routes learned over Link1 and a second route learned over Link2. But I suspect that you will only have the route learned over Link1.

HTH

Rick

[tigist_abe]

Rick

There is no RIP updates when Link1 fails. But when both links are up then there is RIP update as in the following:

FastEthernet0/1

C 172.31.22.0 is directly connected, FastEthernet0/1

C 172.31.2.0 is directly connected, FastEthernet0/1

R 172.31.1.0 [120/2] via 172.31.2.1, 00:00:12, FastEthernet0/1

[120/2] via 172.31.22.1, 00:00:18, FastEthernet0/1

what configuration can I make to enable the my cisco router to be able to communicate with the head office when link1 fails?

Thank you

Tigist

[owaisberg]

Tigist,

I think I've already seen similar setup here

on the forum. I suggest, to avoid secondary

IP limitations associated with RIP routing,

try to configure you fastethernet interface

that facing the switch as a trunk, which will

allow you to have two separate subinterfaces

on the router. Then your RIP announcements will work normally. Switch port facing the router should be configured as trunk too.

Let me know if you need any help with that.

HTH,

OW

[tigist_abe]

owaisberg HTH,

Thank you for your response. I did configure the router with subinterfaces and VLANs I configured VLANs on the switch.

Nothing needs to be configured on the WAN devices.

Finally, the branch can communicate with the Head office when either one of the links fail.

Thank you

Tigist

[owaisberg · Accepted solution]

Tigist,

That's correct the only config required was

on the router and the switch.

Glad it is working now.

Thanks,

OW