Manoj Ghorpade wrote:
Hi,
I have a copy of sniffer pro 4.5 and want to use it to monitor
the WAN
links.
I don't have any WAN hardware for sniffer.
Can anyone guide me on how to make the best use of it for
monitoring
WAN traffic ?
I'm assuming you have decided not to go the more obvious route of purchasing
a WAN module for your analyzer, probably because those modules are so
expensive.
Most analyzers support advanced filtering. If you have an idea of which
traffic passes across the WAN versus which traffic stays local, you can set
up a filter to just look at that traffic. You can even monitor utilization
if you do a little arithemetic to take into account that the analyzer will
probably base the utilization on the Ethernet bandwidth rather than your
actual WAN bandwidth. (Using MRTG and router show commands might be better
for this.)
If you're concerned that packets are getting dropped on the WAN side, you
can study the traffic behavior on the Ethernet sides. Do you see a lot of
retransmissions? If your analyzer is placed in the topology in the right
position, then you can probably assume that retransmissions are occuring
because packets are getting dropped on the WAN link. You can look at the
other side of the link too if this is your own network and see if packets
are indeed not arriving on the other side.
You can also study delay and response time by simply using the Ethernet
analyzer. On the other hand, if you want stats on CRC errors on the WAN
link, you need a WAN analyzer (or use router show commands). If you want to
see Layer 2 WAN packets like LMI or Q.921 or Q.931, you'll need the
appropriate WAN module. Likewise, if you want to see WAN headers such as
Frame Relay, PPP, etc., you'll need a WAN analyzer.
I think it boils down to Howard's question, what problem are you trying to
solve?
For more specific advice, you may want to read the final chapter in my new
book. The chapter is called WAN Troublehsooting for LAN Engineers. You have
to buy the whole book to get the chapter though. Sorry about that. ;-)
Wouldn't it be nice if books were more modular. Anyway, the book is called
Troubleshooting Campus Networks. An Amazon link is:
http://www.amazon.com/exec/obidos/ASIN/0471210137/ref%3Dnosim/opendoornetwinc/002-2801204-8784812
Priscilla Oppenheimer
Regards
Manoj Ghorpade.
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7i=56475t=56442
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