[c-nsp] Weird Routing Behaviour

[Daniel Dib]

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Lin Domingo
Sent: den 13 augusti 2010 05:47
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] Weird Routing Behaviour

>I am having weird routing issues with the T1 circuits. We use /30 subnets
for all T1 circuits, so for customer >X with assigned subnet of
x.x.x.176/30, x.x.x.177 is the serial interface on the ISP end of the
circuit. The >ISP side of the router is defined thusly:

>interface Serial6/0/16:0
> description  XYZ Customer
> ip address x.x.x.177  255.255.255.252
> no ip redirects
> no ip unreachables
> no ip proxy-arp
> encapsulation ppp
> no cdp enable


>Now, I am noticing some weird behaviour:

>(a.) For some reason, the router can not ping (its own) ip  -x.x.x.177
-configured on the serial interface! 
>(b.) Same router can ping the CPE end of the circuit, in this case,
x.x.x.178. '
>(c.) Also, if the circuit is bonded multilink T1, the router can ping its
own ip, but even then, a traceroute >to that IP shows that the router
travels to its own IP by way of the CPE ip!! When pinging its own ip, the
>response time is about 4ms!  When pinging that same ip from a neigbhouring
router, response time is 1ms!


>Now, if I do a "show ip route  ip address x.x.x.177", I get:

>Routing entry for x.x.x.128/25
>  Known via "static", distance 1, metric 0 (connected)
>  Redistributing via eigrp 12125
>  Advertised by eigrp 12125
>  Routing Descriptor Blocks:
>  * directly connected, via Null0
>      Route metric is 0, traffic share count is 1



>Why is the route showing as "directly connected, via Null0"  instead of "*
directly connected, via >Serial6/0/16:0"  ? Again if the circuit is a bonded
multi-link t1, the route shows up correctly as "* directly >connected, via
Multilink10"


>Am I missing something? Someone help please!


>Dominic

Do you have a static /25 pointing to null 0 like a pull down route? Is your
/30 part of this /25? Seems weird that you won't see your /30 in the routing
table. I have also had the experience of not being able to ping a serial
interface I'm not sure why this is but maybe someone has a good explanation
for it. 

/Daniel