SUMMARY:Packet Fragmentation troubles in Sol 2.x

From: Michael Baumann (
Date: Sat May 14 1994 - 01:09:04 CDT

Original Question:
]We have a problem here that I cannot solve, perhaps someone "out-there" can.
]Here is the problem, we have a pair of ACC 4100 BRouters connecting
]two remote sites via microwave. All has been wonderful for 3 years. All
]machines were running SunOS4.1.x, life was good.
]Then I added Solaris 2.3 to two machines. One is an SS10, the other and SS2.
]No patches. Now I have the problem of a ping of data packet size 559 (exactly)
]will fail. Less than this, no problem, more than this no workee. Life is bad.
]This is only true of the 2.3 machines, the 4.1.3 machines remain happy.
]Using snoop, i notice ICMP messages that seem to indicate that the packets
]are being fragmented.
]Is this a known problem with 2.3, and if so how to I fix it?
And the winning answer from Brad Walker:
Turn off ip_path_mtu_discovery.

/usr/sbin/ndd -set /dev/ip ip_path_mtu_discovery 0

I have verified this with the manufactuer of the BRouter - They were a little
shocked to find out just how far out of date my software was. Hey, if it ain't
broke, why fix it? Of course now I gotta fix it as it is broke, but I have a
Michael Baumann
Electus Technology Inc. / Loma Linda University Medical Center
San Bernardino, California. (909)799-8308 |Internet:

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