Some times these problems can be caused by a network loop, ie. a port on
a switch is plugged into another port on the same switch, Depending on
the spanning tree config in your switches (Are they managed?) this can
cause the network to become intermitently unstable. I have also had
situations where a wireless access point will 'steal' Mac addresses. You
can find if this is happening by searching for the Mac address of your
DNS server on the switch when the trouble crops up, if the switch tells
you the mac is on some other port than the one the server is connected
to, you have found the culprit.
Both are long shots, but if your DNS works fine then suddenly quits for
a few minutes, I would doubt there is a problem with the config.
My 2 Cents.
Robert Toole
Sr. Systems Engineer
KN Logistics / Calgary
Shawn wrote:
On Thursday 23 June 2005 21:10, Juan Alberto Cirez wrote:
I haven't done this for a while, but one thing you could do--seeing that
it would be tricky to capture the whole thing w/tcpdump--is try using a
graphic network analyzer, that you give you a graphic representation of
the network traffic over a long period. By looking closely at the peaks
and valleys in the graphs you can then determine when a particular issue
took place; you can then have a deeper look at the log files and search
for that time window...
If you think it is a DNS issue, then maybe a review of the DNS
configuration is in order...
Just for kicks--and if at all possible--try setting one of the secondary
DNS to telus' and see what happens....
If I were you, I'd begin by testing the outside link(telus') and see if
indeed it is an 'internal' problem..then test the router(s); the
firewall; the DNS/DHCP servers; and then the individual boxes...Check
the outside and be sure all is well there before you go all crazy and
tear your own network apart trying to fix a problem that does not exists...
Hope this helps
Thanks Juan.
First, do you have any suggestions on a graphical network analyzer? I've used
EtherApe, but that only shows the current activity. If I could find one that
shows me a graph over time for specific types of traffic, that could be
helpful...
Next, I agree with your suggestion to see if it is a Telus issue first.
Unfortunately, this network must be kept up and running as much as possible.
There's approx 40 people who need this operational through the day. So to
run this test would result in some after hours work, and possible some
automated scripting to try to access the web.... I'll look into doing this
over the weekend maybe.
Keep the ideas coming.. :)
Shawn
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