Date: Tue, 13 Feb 2007 11:25:13 -0500 From: Stephen Clark <Stephen.Clark@seclark.us> To: freebsd-net@freebsd.org Subject: pmtud problem Message-ID: <45D1E669.30402@seclark.us>
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Hello List, We have a setup that looks like the following. pc <-ethernet-> freebsd 4.9 <-pppoe-> internet <-ethernet-> freebsd 6.1 on the freebsd box we have a gre tunnel with a mtu of 1420 feeding into a gif vpn tunnel with a mtu of 1280 ( I know this dumb but it the default value when you create a gif ) feeding into a tun0 with a mtu of 1492. What we see is the packet never makes it to the freebsd 6.1 system. if the pc sends a packet of 1460 bytes with the DF bit set shouldn't the freebsd 4.9 system send back an icmp dest unreachable - fragmentation needed and DF bit set? $ sysctl -a | grep mtu net.inet.tcp.path_mtu_discovery: 1 Now if I change the mtu of the gre to 1412 everything works. Any insight would be appreciated. Thanks, Steve -- "They that give up essential liberty to obtain temporary safety, deserve neither liberty nor safety." (Ben Franklin) "The course of history shows that as a government grows, liberty decreases." (Thomas Jefferson)
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