[c-nsp] MRRU on multilink bundle

[david.ponsdesserre at uk.bnpparibas.com]

hello all .


I have a strange Mrru problem here .  Two routers , Canurtc01 and
Paranrtc06 are linked togeter with a multilink bundle . Thigs are not
working as expecting .
The debug ppp events on Paranrtc06  shows

Unable to add to reassembled pkt in 'casnurtc01'
packet len 1506 > MRRU 1500 in 'casnurtc01' discarding


Paranrtc06
!
The config is here
interface Serial0/0:0
 max-reserved-bandwidth 89
 encapsulation ppp
 tag-switching mtu 1512
 ppp multilink
 ppp multilink group 1

interface Multilink1
..
..
 max-reserved-bandwidth 89
 service-policy output Queuing
 tag-switching mtu 1512
 tag-switching ip
 ppp multilink
 ppp multilink group 1
 no clns route-cache
end
As you can see Tag switching is active as well on the physical interface (
on Casnurtc01 as well)  so i am just wondering if for that reason
Paranrtc06 is receiving pkts with an Mtu of 1506 but because the MRRU is
actually sets to 1500 , the router is unable to reassemble those packets .

To my opinion that should not happens , if you read the following
Before Cisco IOS Release 12.3(7)T, configuring the MRRU option negotiated
on a multilink bundle with the MLP was not possible. Cisco IOS software
always advertised an MRRU default value of 1524 bytes, which meant that the
maximum transmission unit (MTU) of the peer's bundle interface was
restricted to a value of 1524 bytes or fewer if the data transfer was to be
successful. Users who wanted to benefit from MLP features had to accept
limits on the MTU byte size setting.
Look like to default MRRU value for the code
c3745-spservicesk9-mz.123-11.T9.bin should be 1524 bytes ..... not 1500 ???
What am i supposed to do , set the Mrru to 1600 ?
Thanks a lot for you time ,
Best regards .
David


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