Crazy Route Scenario

[eh2os]

Here is the scenario that caused one of my remote offices to lose connectivity to the home office:

Home Office router:

Gi0/0 192.168.1.1

Gi0/1 10.13.251.200

Remote Office Router:

Gi0/0 192.168.1.2

Gi0/1 192.168.48.2

Engineer told HOR the following:

ip route 192.168.1.2 255.255.255.255 10.13.251.25

When he did this, the remote office's connectivity to the home office dropped.  Undoing this route brought the remote office back up.  This was such a rookie mistake, that I couldn't believe it, but the more I thought about it I couldn't exactly explain it.  No production traffic (initiated or response) would source or destin for 192.168.1.2 so why would this break connectivity ?  I would think the route would simply do nothing.  

Thanks in advance.

[Karsten Iwen]

Just a guess (it's obvious that with that little information it's not possible to diagnose the problem):

The HO-router runs a VPN to the RO-router. The destination of the VPN-tunnel is 192.168.1.2 and with that new static route the VPN destination can't be reached any more.

[eh2os]

Thanks for the response.  No VPN.  The config is really that basic.  Brand new connection.  I have Network on Demand layer 2 service from AT&T.  HO Router has interface on 192.168.1.x /24 subnet.  HO is .1, remote office is .2.  No NATing, all static routing.  When my guy added the route mentioned above he killed everything  between the HO and RO.  I'm not thinking it was a routing issue, I am thinking the router behaved in a way I didn't expect when seeing that route.

Basically, the route added told the HO router to take anything destined for 192.168.1.2 /32 and point it inside to my monitoring server on 10.13.251.x /24.  What I don't understand is why would that kill all traffic between HO and RO ?  Remember...........192.168.1.2 is the WAN interface of the RO router.  Thanks in advance.

[acampbell]

Hi,

So on the HOR is there a default static route pointing at
192.168.1.2

The HOR must have WAN link 192.168.1.0/MM network as per interface
Gi0/0. Or even a route to 192.168.48.0 pointing at 192.168.1.2

If the guy addess 192.168.1.2 with a /32 then this become the best route to that host.

ip route 0.0.0.0 0.0.0.0 192.168.1.2 or
ip route 192.168.48.0 255.255.255.255 192.168.1.2

Then he adds
ip route 192.168.1.2 255.255.255.255 10.13.251.25

All ROR bound traffic will now be heading to 10.13.251.25

Regards
Alex