[KLUG Members] some network questions

[Bert Bbbink]

Hi all,

I have a question that I am puzzeled with for some time now. I hope
somebody on this list has major knowledge on this subject.

The network/host part is set by the netmask, what basically means that the
last bit set (from left to right) marks the end of the network part. What
if I set my netmask like 255.254.255.0 ? A easily made typing error.
If again the last bit set from left to right marks the end of the network
part my network ends at the 15th bit. You could also argue that the 24th
bit marks the border.
Is this behavior different along different operating systems? It appears
that routers can't see hosts on an other site if that host has it netmask
wrong.

A second question related with the first, if a number of sites are linked
together via routers, the connection fails when compression is used on the
lines. -unless- rarp is switched on. I can only explain this behavior if
switching compression on means that the networkpart bits are left out in
the transmission. Is this true?

Next to the fact that not sending bytes is the most effective way of
accomplishing less trafic, the routers only need to exchange there network
parts on initialisation.

With rarp switched on both sites are using tables to hold the mac/ip
translation as I am told. But than using rarp should mean even less trafic
is needed, the whole ip-info can be droped on transmission.
But that is not the behavior observed. Switching rarp on increasses the
trafic dramatically. ISDN lines are almost always open instead of closed.
What does make the router decided to open up the lines?

So rarp could decrease the needed bandwith at any time but increases it at
other moments; eg some sort of leveling of traffic.

Also, hosts having there netmask wrong are seen from the other site.
That's nice but following the advice of a telco engineer just to always
use rarp "because it than always works" (he said there standard procedure
was always using rarp), does make a nice bill, but does not make me happy.


greetings,

Bert.