[29419] in North American Network Operators' Group
Re: exchange point media (was: Re: MAE-EAST Moving? ...)
daemon@ATHENA.MIT.EDU (John Hall)
Thu Jun 22 14:33:42 2000
Message-ID: <39525D52.E18B4F13@f5.com>
Date: Thu, 22 Jun 2000 11:39:14 -0700
From: John Hall <j.hall@f5.com>
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To: nanog@merit.edu
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This is a problem for many switches that support non-ethernet interfaces.
RFC1191 does not apply to switches (only routers), but it probably should.
I've run into this problem with switches from Fore and Cabletron. I would
bet that this is a problem for most switches.
JMH
Jeff Haas wrote:
...
> Should one install a (fast|gig)ethernet card into one's Gigaswitch
> and said switch have FDDI interfaces, the switch will go from having
> a 4500+ byte MTU to a 1500 byte MTU. This is even between FDDI card
> to FDDI card on the same switch.
>
> The switch will happily fragment the packet if you leave DF off.
> However, if you turn it on, the switch will drop the packet silently.
> The switch is unable to generate ICMP and route it back to the
> sender.
>
> Given all of this, PMTU-D breaks in these circumstances.
...
> --
> Jeffrey Haas - Merit RSng project - jeffhaas@merit.edu
--
John Hall <j.hall@f5.com> F5 Networks, Inc.
Senior Test Engineer 206-505-0800
It is up to us to produce better-quality movies.
-- Lloyd Kaufman, producer of "Stuff Stephanie in the Incinerator"
