[c-nsp] MTU settings/GRE tunnel

[Karol Mares]

Hi,

On 9/20/07, Nick Kraal <nick at arc.net.my> wrote:
>
> Dear all,
>
> We are setting up tunnels within our network, and are using some
> previous documented configurations for this. We will use this to enable
> virtual P2P BGP sessions to isolate certain parts of our routing table.
> Cheap, temporary, and fast.
>
> interface Tunnel0
>   ip address 192.168.100.9 255.255.255.252
>   no ip unreachables
>   no ip proxy-arp
>   ip mtu 1524
>   tunnel source Loopback1
>   tunnel destination 10.10.10.10
>
> Is there any information/advice/rule-of-thumb on setting the MTU size on
> the tunnel interface?
>
> Thanks in advance,
>
> -nick/



I would use MTU of 1524 (IP  MTU of 1500), so that you will not generate
ICMP packets, and also if you are generating the GRE tunnel, use the tunnel
PMTUD under  tunnel interface.

--
          iso