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Problems with tunnel


I have a tunnel betwen a Cisco 3640 and linux gentoo, the internet acces for the Cisco is from a Riverstone Backbone, so i want migrate that Riverstone backbone to a cisco Backbone (CAT 4507) but the tunnel is presenting problems, i dont have web acces, email, etc, i read and found that the problems is MTU, i tried to change the MTU in the tunnel but present the next error.

IPGW4-VPN(config-if)#mtu 1436
% Interface Tunnel9 does not support adjustable maximum datagram size

so i fix the ip mtu and ip tcp adjust-mss and got the same problem

interface Tunnel9
  bandwidth 2048
ip address x.x.x.x
ip mtu 1436
ip tcp adjust-mss 1436
tunnel source x.x.x.x
tunnel destination x.x.x.x
tunnel mode ipip

when i do a sh interface got

Tunnel9 is up, line protocol is up
  Hardware is Tunnel
  Description: x.x.x
  Internet address is x.x.x.x
  MTU 1514 bytes, BW 2048 Kbit, DLY 500000 usec,
     reliability 255/255, txload 1/255, rxload 1/255

i dont know what else do, i tried to fix the MTU in the tunnel and in the inteface Fasth but got the same problem, please your help how i can fix this, any help is welcome.

thanks in advance.


Cisco Employee

Re: Problems with tunnel

"ip tcp adjust-mss 1436" needs to be smaller than the MTU on the tunnel interface.

I would try "ip tcp adjust-mss 1300" and see if that works.