[c-nsp] mlppp on 2801 with 12.4

[Rodney Dunn]

Please run something later in 12.4 if at all possible.

12.4(1c) would be the very last feature release from
the 12.3(x)T branch.

Drops on the MLPPP bundle come when the bundle detects
congestion on the member links and the output queue fills up.

It can be bursty traffic and if so it's very very hard to
detect. See my emails before about using policing to detect
burst in the archives.

This is common especially if they upgraded the lan side interface
and/or the forwarding speed of the router (faster CPU) can move
packets from the lan to the wan side faster. It makes the
burst more impacting on the lower speed wan side.

Or it could be a bug.

I'd start with an upgrade and/or disable interleave. They
shouldn't need that at T1 speeds.

Rodney

On Mon, Feb 26, 2007 at 06:48:11PM -0800, Mark Kent wrote:
> A dual-T1 customer of ours just replaced his 2501 with a
> 2801 running 12.4(1c).
> 
> I configured multilink ppp as usual, but I am getting some weird
> performance issues and a lot of output drops on the multilink
> interface.  Right now, pushing about 1.3Mbs in 1200pps, the 2801 mlppp
> interfaces shows drops at about 40pps outbound from the 2801, as shown
> by this line:
> 
>    Input queue: 0/75/0/0 (size/max/drops/flushes); Total output  
> drops: 43858
> 
> Config on the 2801 is basically this:
> 
> ip cef
> !
> interface Multilink7
>   ip address x.y.z.82 255.255.255.252
>   no ip redirects
>   ppp multilink
>   ppp multilink interleave
>   ppp multilink group 7
> 
> interface Serial0/2/0
>   no ip address
>   encapsulation ppp
>   no fair-queue
>   down-when-looped
>   ppp multilink
>   ppp multilink group 7
> !
> interface Serial0/3/0
>   no ip address
>   encapsulation ppp
>   no fair-queue
>   down-when-looped
>   ppp multilink
>   ppp multilink group 7
> !
> ip route 0.0.0.0 0.0.0.0 x.y.z.81
> 
> Is the above the canonical MLPPP configuration?
> What causes output drops on a Multilink interface?
> 
> Thanks,
> -mark
> 
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