Multilink issue

Unanswered Question
Mar 16th, 2009

We have some spoke sites connected to HUB location. All the sites are having 2 E1 links which are bundled via Multilink. The issue is when we pump traffic on it the CRC and errors on both the links at spoke site increases and when we unbundled the links it works fine. Also when we ping even with heavy size packet there is no drop, no crc and no errors increases. Also the provider as given the clean chit.

What could be the issue. I have attached the config file.

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Giuseppe Larosa Mon, 03/16/2009 - 08:35

Hello Vishal,

you can use

sh ppp multilink


sh int ser0/0/0:0

sh int ser0/0/1:0

to verify if there are errors related to multilink ppp

you have set

ppp multilink fragment delay 8

this implies a dimension of ppp fragments sent on member links

default value is 30 msecs you have set to 8 msecs


you may have set this for VOIP

to perform a test bypassing fragmentation use

ppp multilink fragment disable

in this way you can see if the issue is related to fragmentation.

you may consider to use the two links as separated parallel L3 links.

Hope to help


vishal_bhugra Tue, 03/17/2009 - 04:23

Thanks giuslar, for the reply

I tried disabling fragmentation at multilink but that did not helped.

I checked that errors are increasing at serial interfaces not on the multilink.

Giuseppe Larosa Tue, 03/17/2009 - 04:27

Hello Vishal,

in this case you should have problems also when using them as standalone links.

Verify with the WAN provider the state of the links

Hope to help


vishal_bhugra Tue, 03/17/2009 - 04:38

Hi giuslar

Our provider has already changed their ring for us and also the mux. We have also changed the module on our router side.

can there be any clocking issue. or something else.

we are having similar issue on all the sites having same set-up.

vishal_bhugra Wed, 04/01/2009 - 23:01

Hi giuslar

Thanks for your kind support. I dont know how but upgrading the IOS helped us in resolving the issue

jasonfaraone Thu, 04/02/2009 - 11:58

Yea, it can be a clocking issue. I've run into this before when using dual port VWIC cards. In my case it was a matter of setting the first ports clock source to line, and the second port to internal. Just co-ordinate this with your carrier so that everything matches up.

I use MLPPP at all of my sites... Your configuration should look something like this.


controller T1 0/0

framing esf

clock source internal

linecode b8zs

channel-group 0 timeslots 1-24 speed 64

description Link1 of Sprint Dual T1


controller T1 0/1

framing esf

linecode b8zs

channel-group 0 timeslots 1-24 speed 64

description Link2 of Sprint Dual T1


This Discussion