[c-nsp] BGP Required MTU Size Between Cisco Devices

[Scott Granados]

I think you're mixing apples and oranges a bit.

Do you mean the BGP session would come up and not stay up?

If so you need to do a
show ip bgp neighbor a.b.c.d | inc data

and view the mss size, make sure that packets of that negotiated size can 
pass over the link.  What you'll see in this case many times is keep alive 
packets not traversing so the link will come up and then drop when the keep 
alive timer is exceeded.

If you mean that traffic would establish, routes would exchange, and then 
the session would stay up but traffic couldn't traverse over 5M/S you've 
probably got something else at work rather than BGP.  If I'm understanding 
what you're saying correctly which I might not be.



-----Original Message----- 
From: Righa Shake
Sent: Thursday, September 22, 2011 2:24 PM
To: Keegan Holley
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] BGP Required MTU Size Between Cisco Devices

I had set my Interfaces on an MTU size of 1600 and BGP was unstable and
could not pass traffic over 5MB.
However when i tested an found that I could pass traffic without any issues
when I eliminate the router.

When I set the MTU to 1500 the BG was up and am now able to pass traffic
without any problem.

Regards,
Righa Shake

On Thu, Sep 22, 2011 at 9:03 PM, Keegan Holley 
<keegan.holley at sungard.com>wrote:

> I think MTU discovery just has to work if you are going to use something
> smaller than 1500 and fragmentation needs to work if you are going to set 
> it
> to something small.  There are other caveats for specific scenarios.
>
> 2011/9/22 Righa Shake <righa.shake at gmail.com>
>
>> Hi,
>>
>> Is there any required MTU Size for Cisco BGP session to work
>>
>> Regards,
>> Righa Shake
>> _______________________________________________
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>>
>
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