route help

[scotlaclair]

I have two locations connected by T1 with cisco router on each end. Each router has a connection to a dsl line from isp. One dsl line has failed and I need to set route to point internet traffic to the other router's dsl line across the T1 connection.

Any help would be appreciated.

[mhussein]

You can configure a gateway of last resort on the failed dsl' router to point to the T1 interface. So if the router is currently configured with:

ip route 0.0.0.0 0.0.0.0

you can change it to:

ip route 0.0.0.0 0.0.0.0

Of course this may be a static and temporary fix. If you post your configs, I am sure someone would be able to give you a more efficient/dynamic config fix.

HTH

Mustafa

[scotlaclair]

This is my config for the two routers, but it doesn't work. I can't ping any web address at site 1 across the T1 and out through the default gateway at site two. A more dynamic config would be great if someone is willing to take on the challenge. I also have two T1 lines between the two locations. It would be great to get the multilink working as it should be.

Any help is much appreciated.

Thank you.

[thisisshanky]

Need a network diagram for more troubleshooting.

[scotlaclair]

Sorry, this is all I can get you at this moment.

Hope this helps somehow.

Thanks.

[mhussein]

Can you traceroute from site 1 to public ip addresses?

We need to find out where traffic is being dropped, is it at router 1, router 2, or ISP 2.

Can you also post the output of show ip route of router 1, to verify that the default gateway is set properly. The ip default-gateway on router 1 is unnecessary and shouldn't have an effect since ip routing is enabled, but it should be removed anyway.

There are some more tweaking to be done, but for now with the current configs, I think the traceroute and router1's routing table would give an idea why traffic is not going to ISP 2.

Let us know how it goes.

[scotlaclair]

I did a tracert and it goes to 185.2.1.3 and then 192.168.0.2 and the I get *. 192.168.0.2 is the serial interface for the T1 on router 2. Attached is the show ip route.

Thank you.

[mhussein]

From the routing table:

Gateway of last resort is 0.0.0.0 to network 0.0.0.0

S* 0.0.0.0/0 is directly connected, Serial0/1:0

So it is not clear -to me at least- how to trace this gateway recursively. I am not sure whether this is a proper default gateway or not.

If possible, let's try:

1. Configure a solid default route so that there is no ambiguity as follows:

replace the existing default route commands on router 1

ip default-gateway 185.2.1.3

ip route 0.0.0.0 0.0.0.0 Serial0/1:0

with the following solid routes:

ip route 0.0.0.0 0.0.0.0 192.168.0.2

ip route 0.0.0.0 0.0.0.0 192.12.25.2

this should create a load-balanced gateway of last resort pointing to router 2's T1 interfaces.

2. Test again - from site 1:

(a) Ping 185.2.2.2 (which is router 2's LAN).

(b) Ping 185.2.2.254 (which is router 2's default gateway, it may not respond if it is firwall.).

(c) Traceroute to 185.2.2.2.

(d) Traceroute to 185.2.2.254.

(e) Traceroute to a public ip address.

Let us now how it goes. There is alot to be said about the existing config and how this problem could be avoided, or if there is an issue with ISP 2 gateway/firewall NAT, but it is better to concentrate on the problem at hand for now.

[olorunloba]

I assume that your ISP has assigned the prefix 185.2.1.0/24 and 185.2.2.0/24 to your individual sites. With the DSL down to one of the sites, do they have a redundant config to direct the traffic for 185.2.1.0/24 to site 2 (which was initially meant for site 1). If not, the ISP would always try to send the traffic through the down DSL, which will not work.

A way round this is to configure NAT at site 2.