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Re: mtu mis-match
On Wed, 19 Mar 2008, ann kok wrote:
Some DSL clients, some are working fine. (browsing...ping ...)
Seems like that when the first packet that exceeds MTU (I guess 1492) on the path is sent, you get a PMTU blackhole. You will see the same problem if you ping with big packets.
As to why some clients work and others do not -- a good question. I have some theories on this point (different behaviour wrt setting DF bit; no MSS clamping and some DSL clients have MTU=1492 exposed to the user, others have a middlebox router which shows MTU=1500; some others).
You may want to check that both ends are receiving ICMP packet too big messages (i.e. a firewall doesn't filter them out).
-- Pekka Savola "You each name yourselves king, yet the Netcore Oy kingdom bleeds." Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings