[c-nsp] Strange Routing..

[Howard Leadmon]

  OK, and in my terrible lack of sleep maybe I am missing something that I
shouldn't be, but here is the issue..

 

I have a 7606 with RSP720's running IOS 15.3(3)S6 at this time.  Across the
Ashburn exchange they use the IP block of 206.126.236.0/22 for peering.  If I
look at the router and ask it for the routing for this block I see:

 

#sho ip route 206.126.236.0

Routing entry for 206.126.236.0/22, supernet

  Known via "connected", distance 0, metric 0 (connected, via interface)

  Routing Descriptor Blocks:

  * directly connected, via Vlan99

      Route metric is 0, traffic share count is 1

 

 

My IP in use on the exchange is 206.126.237.136

 

So if I run a show route on a few peers we connect with, I would expect it to
fall inside the above supernet, and if they are in .236, .238, or .239 they
do, but not if they are part of .237.    As an example:

 

#sho ip route 206.126.236.37

Routing entry for 206.126.236.0/22, supernet

  Known via "connected", distance 0, metric 0 (connected, via interface)

  Routing Descriptor Blocks:

  * directly connected, via Vlan99

 

 

.236 is good..

 

#sho ip route 206.126.237.37

% Subnet not in table

 

.237 is bad..

 

#sho ip route 206.126.238.37

Routing entry for 206.126.236.0/22, supernet

  Known via "connected", distance 0, metric 0 (connected, via interface)

  Routing Descriptor Blocks:

  * directly connected, via Vlan99

 

.238 is good, as well at .239..

 

If I look at the routes I see the router seems to be injecting a local /32
which doesn't make a lot of sense to me either:

 

#sho ip route 206.126.237.0

Routing entry for 206.126.237.0/32, 1 known subnets

  Attached (1 connections)

L        206.126.237.136 is directly connected, Vlan99

 

 This is causing connection issues for some of the peers for sure, and a
static route for the /24 will add it to the routing table, I am at a total
lost as to why it's not already present with the /22 in the table, and with
the fact the interface to the IX shows with a mask of 255.255.252.0.   All of
my IPv6 is great, just this one issue with IPv4 driving me batty.

 

Any suggestions or advice most welcome..

 

 

---

Howard Leadmon 

PBW Communications, LLC

 <http://www.pbwcomm.com> http://www.pbwcomm.com