[c-nsp] BGP sessions won't establish.

[Tolstykh, Andrew]

Cogent runs two BGP sessions because edge router that terminates the
initial sessions does not have a full view and will only advertise /32
route of the "real" BGP peer. Our BGP deployment with Cogent was
flawless; they were very helpful and turned everything up in no time.

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Steve Bertrand
Sent: Monday, June 30, 2008 5:46 PM
To: Roy
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] BGP sessions won't establish.

Roy wrote:
> Just to bring everybody up to date, the ISP keeps saying its something

> we are doing.  To eliminates any quirks, we have a spare router
directly 
> connected to the metro ethernet box now.  All the hardware is
different 
> and we have tried several version of IOS.  The config has been
stripped 
> down to bare bones.  I have attached the relevant portion.  The first 
> session (the neighbor ending in .233) comes up.  The other one (ending

> in .18) fails
> 
> interface Loopback0
> ip address 3xx.xx.68.19 255.255.255.255

...just out of curiosity, is 3xx a typo here, or do you have your first 
octet accidentally set to > 300 in the running config?

> neighbor yyy.yyy.yyy.18 ebgp-multihop 10
> neighbor yyy.yyy.yyy.18 update-source Loopback0

I had a discussion not too long ago regarding eBGP and loopbacks, and 
even though it will work, why are you doing it?

Without knowing the live IP for your loopback, it's hard to test, but 
can you ping the loopback address from outside of your network? Perhaps 
that address is not routed correctly on the global network, and they 
simply can't find a path back to it.

Do you see this loopback /32 in your route table? Is it confirmed 
reachable from a remote network? If both are true, does it help if you 
use update-source ip_of_loopback, as opposed to the interface name?

I've never applied an IP to lo0 before... does it make a difference if 
you reset lo0, and use another loopback interface instead?

> The state is Active and never changes.

...a session can not be established at the transport layer, let alone 
BGP communicating. Does 'sh logging' provide any info after enabling bgp

debug?

Can you ask the provider to at minimum provide to you their end of the 
relevant config for review/comparison?

Steve
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