[c-nsp] 2851 and full BGP

[Church, Charles]

Oh, yeah.  Sorry, I didn't catch the 'WAN' part of it the first time.
That does make MTU a possibility.  But didn't he get like 20% of his
routes before the error message?  Since it was 12.4(20)T (pretty
bleeding edge), I'd lean towards that still.  I'd think that an MTU
problem would show up way before you got to 20%.  Does BGP set the DF
bit?

Chuck

-----Original Message-----
From: Paul Cosgrove [mailto:paul.cosgrove at heanet.ie] 
Sent: Monday, August 11, 2008 4:33 AM
To: Church, Charles
Cc: mtinka at globaltransit.net; cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] 2851 and full BGP


Hi Chuck,

Jay will be able to clarify, but I took the following to mean that the 
two are separated via third party infrastructure: "two 2851s connected 
to each other over gigabit Ethernet WAN".

May well be a bug though.

Paul.

Church, Charles wrote:
> Wasn't the original problem the iBGP connection over his own network?
Sounds like a bug more than anything else.
> 
> Chuck
> 
> ----- Original Message -----
> From: cisco-nsp-bounces at puck.nether.net
<cisco-nsp-bounces at puck.nether.net>
> To: mtinka at globaltransit.net <mtinka at globaltransit.net>
> Cc: cisco-nsp at puck.nether.net <cisco-nsp at puck.nether.net>
> Sent: Sun Aug 10 15:52:03 2008
> Subject: Re: [c-nsp] 2851 and full BGP
> 
> 
> Keep in mind that if the peerings are not between directly connected
IP, 
> disabling PMTUd for BGP will cause it to use an MSS of 536 bytes.
> 
> You could check the achievable MTU using extended pings with the DF
bit 
> set, and compare it with the segment size listed by BGP before you 
> decide whether to make that change.
> 
> Paul.
> 
> Mark Tinka wrote:
>> On Saturday 09 August 2008 10:28:40 Jay Nakamura wrote:
>>
>>   
>>> Any ideas on what could be causing this issue?  Is there
>>> a better IOS version to use?
>>>     
>> Sounds like an MTU issue.
>>
>> Try disabling TCP PMTUd for BGP and see if that helps:
>>
>> router bgp 1234
>>  no bgp transport path-mtu-discovery
>>
>> If that works, consider checking with your provider on the 
>> supported MTU, end-to-end, and adjust your interface MTU if 
>> it helps.
>>
>> Cheers,
>>
>> Mark.
>>   
>>
------------------------------------------------------------------------
>>
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