[j-nsp] GRE Tunnel bet JUNIPER and CISCO

masood at nexlinx.net.pk masood at nexlinx.net.pk
Wed Nov 3 09:41:20 EDT 2010

Generally, this issue is related to MTU and fragmentation. If you have a
problem with loading web-pages and slow tcp response, you better try
adjusting tcp-mss settings on your cisco router. You can use the following
command under tunnel interface, most of the time it works for me :)

interface tunnelX
ip tcp adjust-mss 1436

On juniper side you can add the following knobs under the gr interface conf

gr-x/x/x {
unit x {
  tunnel {



> People,
> We are trying to close a GRE tunnel between juniper and Cisco routers
> without success.
> We have tried a lot of MTU configurations but the traffic is suffering a
> lot ... sometimes slow, sometimes do not open some pages.
> Have you ever configured something like this before ?
> Any tip ou configuration related to best practices ?
> Thanks a lot,
> Giuliano
> _______________________________________________
> juniper-nsp mailing list juniper-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/juniper-nsp

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