nanog mailing list archives
Re: can I ask mtu question
From: Sam Stickland <sam_mailinglists () spacething org>
Date: Tue, 03 Feb 2009 16:42:19 +0000
Niels Bakker wrote:
* sam_mailinglists () spacething org (Sam Stickland) [Tue 03 Feb 2009, 13:04 CET]:Sorry, I should had clarified. I meant mismatched host MTUs within a jumbo MTU supporting L2 domain.For what it's worth, TCP will negiogate MSS and will work with mismatched MTU in a single LAN segment.NoMachine 1 -- switch with 1500 byte MTU -- switch with smaller MTU -- switch with 1500 byte MTU -- machine 2Same situation as when you have IP routers with smaller MTUs in the path that also do not send ICMP Fragmentation Needed errors (or those are dropped on the way to you)If you configure one of those machines with an MTU equal to or smaller than the smallest MTU in the path then yes TCP (assuming MSS option is used) won't send packets that happen to be too big, but again, same story as for routers vs on a LAN. The problem isn't that machine 1 and 2 in the above example disagree on MTU, the problem is that equipment in the path disagrees on the MTU and cannot (in the case of switches) send notifications of such, or those will not arrive (in the case of stupid firewall admins in control of networks).
Sam
Current thread:
- Re: can I ask mtu question Michael Dillon (Feb 01)
- <Possible follow-ups>
- Re: can I ask mtu question Bill Stewart (Feb 03)
- Re: can I ask mtu question Sam Stickland (Feb 03)
- Re: can I ask mtu question Niels Bakker (Feb 03)
- Re: can I ask mtu question Sam Stickland (Feb 03)
- Re: can I ask mtu question Niels Bakker (Feb 03)