nanog mailing list archives
Re: Ethernet NAPs (was Re: Miami ...)
From: Leo Bicknell <bicknell () ufp org>
Date: Wed, 22 Aug 2001 19:43:43 -0400
I just have to speek up that this is all very well and good, but it's also a good way to make a NAP that doesn't work. _ALL_ devices on a layer-2 fabric need to have the same MTU. That means if there are any FastEthernet or Ethernet connected members 1500 bytes is it. It also means if you pick a larger value (4470, 9k) _ALL_ members must use the same value. If you don't, the behavior is simple. A 9k MTU GigE arps for a 1500 byte FastEthernet host. Life is good. The TCP handshake completes, life is good. TCP starts to send a packet, putting a 9k frame on the wire. Depending the switch, the switch either drops it as over MTU for the FastEthernet, or the FastEthernet card cuts it off at 1500 bytes, and counts it as an errored frame (typically with a jabber or two afterwards) and no data flows. A larger MTU is a fine plan, but make sure if you try that anywhere that the switch is set for the larger sizes and all devices are capable of that larger frame size, or you're in trouble. -- Leo Bicknell - bicknell () ufp org Systems Engineer - Internetworking Engineer - CCIE 3440 Read TMBG List - tmbg-list-request () tmbg org, www.tmbg.org
Current thread:
- Maimi Nap of the America's Vinny India (Aug 22)
- RE: Maimi Nap of the America's Daniel Golding (Aug 22)
- RE: Ethernet NAPs (was Re: Miami ...) RJ Atkinson (Aug 22)
- RE: Ethernet NAPs (was Re: Miami ...) Mikael Abrahamsson (Aug 22)
- RE: Ethernet NAPs (was Re: Miami ...) RJ Atkinson (Aug 22)
- Re: Ethernet NAPs (was Re: Miami ...) Leo Bicknell (Aug 22)
- Re: Ethernet NAPs (was Re: Miami ...) Marc Slemko (Aug 22)
- Re: Ethernet NAPs (was Re: Miami ...) Leo Bicknell (Aug 22)
- Re: Ethernet NAPs (was Re: Miami ...) Dan Hollis (Aug 22)
- Re: Ethernet NAPs (was Re: Miami ...) Miquel van Smoorenburg (Aug 23)
- Re: Ethernet NAPs (was Re: Miami ...) Mikael Abrahamsson (Aug 23)
- RE: Ethernet NAPs (was Re: Miami ...) RJ Atkinson (Aug 22)
- RE: Maimi Nap of the America's Daniel Golding (Aug 22)
- Re: Ethernet NAPs (was Re: Miami ...) RJ Atkinson (Aug 22)
- Re: Ethernet NAPs (was Re: Miami ...) Mikael Abrahamsson (Aug 22)
- Re: Ethernet NAPs RJ Atkinson (Aug 23)
- Re: Ethernet NAPs (was Re: Miami ...) John Kristoff (Aug 23)
- Re: Ethernet NAPs (was Re: Miami ...) Mikael Abrahamsson (Aug 23)