From: "Berg, Ivan" <iberg@montana.edu>
This is not quite appopriate for this list since these are general
networking questions however I cannot seem to find an answer anywhere else
on the net.
Since most of you are networking professionals I thought I would give it a
try.
1. Sending a ping to the broadcast address of several subnets results in
DUP packets from almost every responding hosts. The router of these subnets
has directed broadcasts turned on. Other routers have directed broadcasts
turned off and thus I can not reach them from where I am at. The man page
for ping states this:
DUPLICATE AND DAMAGED PACKETS
Ping will report duplicate and damaged packets. Duplicate packets
should
never occur, and seem to be caused by inappropriate link-level retrans-
missions. Duplicates may occur in many situations and are rarely (if
ev-
er) a good sign, although the presence of low levels of duplicates may
not always be cause for alarm.
Now, this does not sound good, could this be normal?? cause for alarm?? what
could be causing it.
2. I have read networking books that state when using a classfull routing
protocol such as RIP that you should not use masks other than the standard
class ones. They say you could possibly do it but that the mask should
always be larger than what you are using by default on other equipment. For
instance, if you have a class C subnet with a mask of 24, then it states
that you should only use masks > 24. e.g. DONT use a 23 bit net mask. My
question is: why is this bad?? It doesn't seem to cause problems. For
instance, on network using RIP, we want subnet with 512 hosts(23 bit
netmask), since all hosts don't have netmask set properly, two routes are
used. For example, 192.168.1.0/23 would be the proper way, however, you can
also use 192.168.1.0/24 and 192.168.2.0/24 since RIP doesn't know about 24
bit netmask and this will also work. Of course, you lose 192.168.2.0 and
192.168.1.255 as valid addresses, but it seems to work.
Why is this bad??
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