BGP neighbor/configuration testing

Mon Nov 25 23:07:28 UTC 2013

All Cisco/Cisco, I don't have a Juniper here to test with

mismatch AS
*Apr  9 00:31:47.691: %BGP-3-NOTIFICATION: received from neighbor 10.250.254.253 2/2 (peer in wrong AS) 2 bytes 6A39

mismatch neighbor IP address
no logged error

MTU mismatch
no logged error, session remained up

Subnet mask mismatch
session remained up, no logged error

I haven't created the multihop scenario to see the error messages.

None of these issues caused the (authentication failure).

>________________________________
> From: Chuck Anderson <cra at WPI.EDU>
>To: nanog at nanog.org 
>Sent: Monday, November 25, 2013 11:10 AM
>Subject: Re: BGP neighbor/configuration testing
> 
>
>Authentication failure might mean (without knowing for sure which on
>Cisco):
>
>- mismatch AS numbers
>- mismatch neighbor IP addresses
>- multihop/TTL issues
>- MTU issues
>
>On Mon, Nov 25, 2013 at 11:06:33AM -0800, Eric A Louie wrote:
>> That's a natural first impression but there are no passwords configured on the BGP session on either router.  I know it looks like an authentication error but it's a "misnomer" (at least from the searches I did on the error message).  From the sequence of messages, we get Established and 2 seconds later the session Closes.  The reason for the Close may lead us to the solution.
>> 
>> I'm reluctant to turn on debug bgp because this is a live production router, and if I hose it, there will be a lot of 'splainin to do [1]
>> 
>> [1] http://www.quotecounterquote.com/2011/05/lucy-you-got-some-splainin-to-do.html
>> 
>> 
>> 
>> 
>> 
>> >________________________________
>> > From: Daniel Rohan <drohan at gmail.com>
>> >To: Eric A Louie <elouie at yahoo.com> 
>> >Cc: Joe Abley <jabley at hopcount.ca>; "nanog at nanog.org" <nanog at nanog.org> 
>> >Sent: Monday, November 25, 2013 10:55 AM
>> >Subject: Re: BGP neighbor/configuration testing
>> > 
>> >
>> >
>> >Seems like:
>> > 
>> >Nov 25 06:28:34.837 pacific: %BGP-3-NOTIFICATION: received from neighbor xxx.118.92.149 2/5 (authentication failure) 0 bytes
>> >>
>> >should be a good starting place. I'm assuming you've already discussed auth keys with your provider and if everyone is putting that in correctly, I'd suggest turning on debugging to see what exactly that message is all about. 
>> >
>> >
>> >Dan 
>
>
>
>