[c-nsp] Multilink PPP Problems

[Jon Lewis]

On Fri, 4 Nov 2005, Adam Piasecki wrote:

> I've been through just about every thread on this site, yet seem to be at a
> dead end. We have 4T1's configured as a MLPPP. I'm currently loosing
> anywhere from 10% - 20% packet loss across the MLPPP Group. I get 0% packet
> loss when the link is running 1mb/s or below. It doesn't seem to be a CPU or
> bandwidth issue. We have other Multilink groups in the same router that
> don't have this problem. I do notice that the T1's are taking on more
> interface resets then others. Could this be bad hardware??? All of the T1's

Interface resets would mean you're losing the T1's from time to time, 
which would explain the packet loss if they're that frequent.  Usually, 
that means there's a problem with the circuits/CSU/wiring.

> Reply from X.X.X.X: bytes=32 time=2218ms TTL=243
> Request timed out. -- > discarded fragments/bytes increases
> Request timed out. -- > discarded fragments/bytes increases

Have you tried disabling fragmentation?


> interface Serial1/0/0:0
> bandwidth 1544
> no ip address
> ip access-group AZ-IN1131114133 in
> ip access-group AZ-IN1131114133 out
> encapsulation ppp
> no ip route-cache
> load-interval 30
> tx-queue-limit 26
> down-when-looped
> no fair-queue
> ppp multilink
> multilink-group 2

Why are you applying ACLs to member interfaces of a MLPPP group?  I doubt 
they have any affect, but I'd get rid of them.  I'm also not sure why 
you'd put no ip route-cache in the member interfaces, but I suspect it 
also has no effect.

You could eliminate MLPPP from the mix and just configure these as HDLC 
and use cef per-packet load sharing (per-destination if they're doing 
VOIP) and see if you still have interface resets, odd latency, and packet 
loss.

----------------------------------------------------------------------
  Jon Lewis                   |  I route
  Senior Network Engineer     |  therefore you are
  Atlantic Net                |
_________ http://www.lewis.org/~jlewis/pgp for PGP public key_________