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Multilink PPP issue

 

 

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jfmays at launchpad

May 4, 2011, 2:28 PM

Post #1 of 2 (2538 views)
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Multilink PPP issue

Trying to bond together two pppoe links into one multilink bundle. The links admittedly are not the same speed, one goes through a DSL modem bridged ethernet connection that has two bonded DSL lines, the other goes through a single-DSL line bridged modem.

The links bundle alright, but the performance sucks. Console output on the router whenever a significant amount of data is being downloaded shows....

4d23h: Vi2 MLP: Lost fragment 7641 (all links out of sequence)
4d23h: Vi2 MLP: Begin bit lost, discard fragment 7642
4d23h: Vi2 MLP: Lost fragment 7697 (all links out of sequence)
4d23h: Vi2 MLP: Discard reassembled packet
4d23h: Vi2 MLP: Lost fragment 76BD (all links out of sequence)
4d23h: Vi2 MLP: Discard reassembled packet
4d23h: Vi2 MLP: Lost fragment 76D9 (all links out of sequence)
4d23h: Vi2 MLP: Discard reassembled packet
4d23h: Vi2 MLP: Lost fragment 76E5 (all links out of sequence)
4d23h: Vi2 MLP: Discard reassembled packet
4d23h: Vi2 MLP: Lost fragment 7751 (all links out of sequence)
4d23h: Vi2 MLP: Discard reassembled packet
4d23h: Vi2 MLP: Lost fragment 775B (all links out of sequence)
4d23h: Vi2 MLP: Discard reassembled packet

... and so on. These messages don’t occur if I only have one link in the bundle, and each link performs at the speed it should by itself. The errors only occur when both links are in the bundle, and then the speed is also at the floor. Is this because of the fact that two different link speeds are at work? Or could there be another cause in the mlppp config? Is there a way to weigh the links so that the bonded dual line DSL link carries twice the traffic of the single line DSL link?

Joe Mays


lee.e.rian at census

May 4, 2011, 4:57 PM

Post #2 of 2 (2391 views)
Permalink
Re: Multilink PPP issue [In reply to]

If I was determined to make multilink PPP work over different speed links
the first thing I'd try is disabling fragmentation - eg

interface Multilink1
ppp multilink
ppp multilink group 1
ppp multilink fragment disable

but my only experience with multilink ppp is bundling T1s together between
routers, so the suggestion might very well be worth exactly what you paid
for it :)

Regards,
Lee





From: "JoeMays" <jfmays [at] launchpad>
To: <cisco-nas [at] puck>
Date: 05/04/2011 05:30 PM
Subject: [cisco-nas] Multilink PPP issue
Sent by: cisco-nas-bounces [at] puck



Trying to bond together two pppoe links into one multilink bundle. The
links admittedly are not the same speed, one goes through a DSL modem
bridged ethernet connection that has two bonded DSL lines, the other goes
through a single-DSL line bridged modem.

The links bundle alright, but the performance sucks. Console output on the
router whenever a significant amount of data is being downloaded shows....

4d23h: Vi2 MLP: Lost fragment 7641 (all links out of sequence)
4d23h: Vi2 MLP: Begin bit lost, discard fragment 7642
4d23h: Vi2 MLP: Lost fragment 7697 (all links out of sequence)
4d23h: Vi2 MLP: Discard reassembled packet
4d23h: Vi2 MLP: Lost fragment 76BD (all links out of sequence)
4d23h: Vi2 MLP: Discard reassembled packet
4d23h: Vi2 MLP: Lost fragment 76D9 (all links out of sequence)
4d23h: Vi2 MLP: Discard reassembled packet
4d23h: Vi2 MLP: Lost fragment 76E5 (all links out of sequence)
4d23h: Vi2 MLP: Discard reassembled packet
4d23h: Vi2 MLP: Lost fragment 7751 (all links out of sequence)
4d23h: Vi2 MLP: Discard reassembled packet
4d23h: Vi2 MLP: Lost fragment 775B (all links out of sequence)
4d23h: Vi2 MLP: Discard reassembled packet

... and so on. These messages don’t occur if I only have one link in the
bundle, and each link performs at the speed it should by itself. The
errors only occur when both links are in the bundle, and then the speed is
also at the floor. Is this because of the fact that two different link
speeds are at work? Or could there be another cause in the mlppp config?
Is there a way to weigh the links so that the bonded dual line DSL link
carries twice the traffic of the single line DSL link?

Joe Mays
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