Re: ICMP's & IP src addrs


Charles Hedrick (aramis.rutgers.edu!athos.rutgers.edu!hedrick@rutgers.edu)
17 Sep 88 01:23:10 GMT


We've certainly been bitten by hosts that respond to broadcasts
inappropriately, so I'm sympathetic with the idea of being very
conservative in responding to ICMP broadcasts. But let's not go too
far. Kent England says you are never allowed to respond to a
broadcast by sending an ICMP, even if the source of the broadcast is
an ICMP. I think what should be said is that you never respond to a
broadcast by sending an ICMP *error* message. If the original
broadcast is one of the ICMP queries, and the query is well-formed,
you can certainly send the corresponding response. Otherwise you
couldn't broadcast an ICMP net mask request and expect to get a
response. I have mixed feelings about broadcast ICMP echo requests.
If you do it very much, it could produce very bad results. However I
can also think of situations where I would want to be able to do it.
So I'm inclined to say that it should be legal to respond to a
broadcast ICMP echo request. If the host requirements RFC says what
you said, I think Bob Braden should think again. Either that or come
up with some other way to find out your net mask...



This archive was generated by hypermail 2.0b3 on Thu Mar 09 2000 - 14:43:30 GMT