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Re: Stumper
- From: Marshall Eubanks
- Date: Tue Jan 21 17:42:07 2003
Could this be a packet size issue ?
You might try
ping -s
and see if, say, 1500 byte and 4500 byte packets get through.m
On Tuesday, January 21, 2003, at 05:25 PM, Mark J. Scheller wrote:
I have run into a problem that has me completely stumped, so I'm
tossing it
out to NANOG for some help.
Before I lay out the specifics, I'm not trying to point fingers at any
particular ISP or vendor here, but this problem only exhibits itself in
very
specific configurations. Unfortunately, the configuration is common
enough as
to get unwanted attention from the higher-ups.
Here's the particulars:
Users that have Verizon DSL and a Linksys cable/DSL router have
difficulties
accessing sites on my network -- whether they are trying with http,
https,
smtp, pop3, ssh, ftp, etc., etc. Oh, but pings seem to be fine. Low
latency,
no loss. This is true even for access to a server brought up in the
DMZ, to
keep the firewalls out of the equation.
Doing some packet sniffing on the ethernet side of my router, I could
see
specific http requests never showed up (and the user saw the broken
image
icon). This was for an mrtg graph page with +/- 30 images. I saw the
request
for almost all the image files, save for one and the user reported the
broken
image icon for the one. So this looks and smells like a packet loss
issue..... but who/where/how?
Taking the Linksys out of the pictures (connecting their PC directly to
the
Verizon DSL modem) makes the problem go away.
These same users report no trouble whatsoever accessing many other
common
sites across the internet.
Here's another interesting data point: when one user runs Morpheus (on
any machine in his home network) he then has absolutely no problems
accessing
servers/services on my network.
Other users with Linksys routers and, say cable modem, do not have this
problem!
So I'm looking for some pointers. What could I have done to my edge
router (a
Cisco 3640 if that helps any) that would make it drop packets from
Verizon DSL
customers with Linksys routers so long as they aren't running Morpheus?
Mark J. Scheller ([email protected])
Regards
Marshall Eubanks
T.M. Eubanks
Multicast Technologies, Inc
10301 Democracy Lane, Suite 410
Fairfax, Virginia 22030
Phone : 703-293-9624 Fax : 703-293-9609
e-mail : [email protected]
http://www.multicasttech.com
Test your network for multicast :
http://www.multicasttech.com/mt/
Status of Multicast on the Web :
http://www.multicasttech.com/status/index.html
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