[c-nsp] MTU change on data link layer and connection degradation/loss

[Andrew Miehs]

On 15/08/2011, at 2:39 AM, Martin T wrote:
> I have a following network topology:
> 
> C3750G-12S[Gi1/0/12] <-> [ge-0/0/0]Juniper M10i[ge-1/0/0] <->
> [Po1]Cisco 4506[Gi2/6] <-> [Gi1/0/1]C3750G-12S
> 
> Is it a best practise to use the largest possible value
> on all interfaces or find out the largest supported MTU on the circuit
> and use this for all the interfaces?

This depends on your traffic.

Do you have servers connected to the 3750Gs that need to talk to another on the same switch with large amounts of traffic?
Then setting a large MTU on the 3750G will be to your advantage. Setting all interfaces to the "smallest" value, will ensure that you don't have any PMTU problems should someone have the bright idea of dropping ICMP packets.

If possible, try to keep your MTU at least large enough so that should someone decide to tunnel traffic that it will still be larger than 1500 bytes.


Regards

Andrew