[c-nsp] Cisco IOS DHCP server && setting MTU size

[Joe Maimon]

Tim Franklin wrote:

>>Joe Maimon already replied that you can put it only on the PPPoE 
>>interface. We have no experience with that although it may be a 
>>better method. I simply do not know.
> 
> 
> Isn't that the case for 'mtu / ip mtu' rather than 'ip tcp mss-adjust'?

This should happen automatically on pppoe dialer interfaces on ethernet 
interfaces.

> 
> We do the former on tunnel / PPPoX dialer / whatever else where we're stuck
> with a link in the middle that won't pass 1500 bytes, and *usually* PMTUD
> does exactly what it's supposed to.
> 
> The problem is when damnfool "security experts" drink from the "all ICMP is
> Eeeeevil!" kool-aid and block the responses...

This is what ip tcp adjust-mss works around. Its a hack. However, its 
the most effective and elegant hack currently in use by just about 
everyone. It also goes under other names such as clamp_mss.

> 
> Regards,
> Tim.
>