Re: ICMP's & IP src addrs


jmg (mcvax!cernvax!jmg@uunet.uu.net)
26 Sep 88 16:44:02 GMT


>>Now wait a minute....It's one thing to reply to the local IP broadcast
>>address - it's another thing to use the Ethernet broadcast address as
>>your source address! DEC Lanbridges don't look at anything higher than
>>that. They should ignore multicast/broadcast addresses as a source
>>address (although I don't really know if they do).
>>
>Doug Nelson
>Michigan State University

If you have LANBridges with version 2 of their software then it is
true that they can be got into the state where no broadcasts go
through (but multicasts are OK).
This bug was not in version 1.0. Of course, both versions had bugs if
you use RBMS to change costs of lines, bridges etc.
The broadcast problem certainly is provoked if the LANBridge sees a
packet whose source address is ffffffffffff. To clear it the bridge
has to be reinitialised.
The symptoms are obvious: new tcp/ip connections fail, but old
connections, plus ones where the ethernet address is already in cache,
continue to work, as does DECNET. Thus, all the people with Vaxstations
do not want the Ethernet touched, for fear that their station will need
rebooting, but all the TCP/IPersons want it fixed. How to become
unpopular in one easy lesson!

--
 _ _  o	|	      __		    |	  _ _  o	|	      __		    |	 jmg@cernvax.uucp
| | |	|     _	     /	\  _   __  _   __  _|	 jmg@cernvax.bitnet
| | | |	|_)  /_)     |	__/_) |	(___\ |	(_/ |  J. M. Gerard, Div. DD, CERN,
| | |_|_| \_/\___    \__/ \___|	  (_|_|	  \_|_ 1211 Geneva 23, Switzerland



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