MTU breakage in f20

Mon Nov 3 00:16:54 UTC 2014

It looks like something broke recently that severely limits the MTU in
Fedora 20 when running under NM.  Are other people seeing this too?
Here I'm pinging my upstream lan-to-wan gateway.  A 1200 byte ping fails
while a 500 byte one succeeds.  I see the same thing when pinging
between two identical, fully up-to-date f20 systems.

   wolfgang at arbol ~]$ ping -s 1200 gw
   PING gw.wsrcc.com (192.168.35.1) 1200(1228) bytes of data.
   ^C
   --- gw.wsrcc.com ping statistics ---
   3 packets transmitted, 0 received, 100% packet loss, time 2000ms

   [wolfgang at arbol ~]$ ping -s 500 gw
   PING gw.wsrcc.com (192.168.35.1) 500(528) bytes of data.
   508 bytes from gw.wsrcc.com (192.168.35.1): icmp_seq=1 ttl=64 time=0.503 ms
   508 bytes from gw.wsrcc.com (192.168.35.1): icmp_seq=2 ttl=64 time=0.460 ms
   508 bytes from gw.wsrcc.com (192.168.35.1): icmp_seq=3 ttl=64 time=0.456 ms
   508 bytes from gw.wsrcc.com (192.168.35.1): icmp_seq=4 ttl=64 time=0.454 ms
   ^C
   --- gw.wsrcc.com ping statistics ---
   4 packets transmitted, 4 received, 0% packet loss, time 3001ms
   rtt min/avg/max/mdev = 0.454/0.468/0.503/0.025 ms
   [wolfgang at arbol ~]$ 

-wolfgang