Path MTU netstat

Sergey _lion_2000 at
Wed Feb 27 11:39:53 UTC 2008

I want to see currently discovered Path MTU.

I tried netstat -rnaW, but it doesn't show any cloned routes, but i clearly
see Path MTU discovery working, by watching tcpdump tracing. An application
sends full sized packet with DF bit, receives ICMP Unreach Frag message and
retransmits downsized packet again.

I need this, because there is another  6.2-RELEASE-p3  host, which doesn't
perfom Path MTU discovery, although:
# sysctl -a | grep path_mtu
net.inet.tcp.path_mtu_discovery: 1

I tried disabling firewall, simplifying routing, but none helps.

Anyone help?

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