[c-nsp] no packet loss until BGP is brought up?!?

[Vinny Abello]

At 10:02 PM 5/12/2005, Pete Templin wrote:
>Dennis Nugent wrote:
>
> >   An existing client just changed their equipment to a Diamond msm3
> > We have a Cisco 6503 with a Supe2msfc2
> > Cat5 cross-connect to them for about a year with no issues with their old
> > router.  When we do extended pings to the new  interface, there is no
> > packet loss.
> > As soon as he brings up BGP, we get 17 - 25% packet loss.  Turn off BGP,
> > and packet loss goes back to 0.
> > He has changed interfaces, etc.  When his BGP is up, there is no 
> issue with
> > CPU or memory in his Diamond.
> >
> > He is also doing BGP with other upstreams, and states that he is 
> not seeing
> > any packet loss to the other upstream providers.
> >
> > Has anyone else seen anything like this?  Besides the obvious, any
> > recommendations?
>
>Had a very similar situation where we had a duplex settings mismatch.
>Pings weren't enough to find it, but the traffic load "in production"
>was more than capable of exposing it.

We saw something like this on a point to point DS3. Didn't start 
seeing problems until there was load on it with BGP turned up. 
Problem turned out to be the other side's insistence that scrambling 
wasn't necessary on the circuit... until I convinced them to turn it 
on and the problem was fixed. Of course this is apples and oranges, 
but your situation reminded me of this. We've seen this also on 
Ethernet with duplex mismatches as well. If you can only do half 
duplex for some horrible reason, you're likely running into excessive 
collisions because of the amount of conversations taking place. 
Otherwise, the duplex is probably just mismatched.

Vinny Abello
Network Engineer
Server Management
vinny at tellurian.com
(973)300-9211 x 125
(973)940-6125 (Direct)
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