From: john matijevic (john.matijevic@gmail.com)
Date: Sun Aug 07 2005 - 15:23:38 GMT-3
Hello Sean,
Im not sure I fully understand what the problem is? You had mentioned that
the exchange server was upgraded and the upgrade did not go as planned, and
the finger is being pointed at the network as the problem. What about the
upgrade that did not go as planned? What exactly is the problem?
Sincerely,
John
On 8/7/05, cacca mucca <caccamucca@hotmail.com> wrote:
>
> Like I said, it is the network issue until proven otherwise. This is why
> we
> have to snif wasting all of our time to help the server and application
> team
> out.
>
> >From: Wes Stevens <wrsteve33-gsccie@yahoo.com>
> >Reply-To: Wes Stevens <wrsteve33-gsccie@yahoo.com>
> >To: cacca mucca <caccamucca@hotmail.com>, ccielab@groupstudy.com
> >Subject: RE: Real world finger pointing at network
> >Date: Sun, 7 Aug 2005 10:25:48 -0700 (PDT)
> >
> >I have 23 years in networking. I started using
> >protocol analysers before you got your hands on your
> >first pc. I have used ethernet sniffers for 12 years
> >and token ring sniffers before that. My team spends
> >probably 1/4 of it's time doing sniffs for the server
> >group and I catch the hard ones as I have been
> >sniffing microsoft for years and know the protocols
> >well. It is not that I can't find the problems, the
> >issue that most of them are not caused by the network.
> >It is an application that breaks protocol or that was
> >developed to run on a lan and cannot handle normal
> >network delays. Why is it that I have to do sniffs to
> >fix server problems all the time? The reason is that
> >the server guys do not understand networking and
> >Microsoft has shit tools for troubleshooting.
> >
> >Your server managers may buy your crap, but management
> >here knows better. We have to do sniffs because that
> >is the only way the problems get fixed.
> >
> >Wes #11480 R&S and a MCSE from 1994 and the experince
> >to back them up.....
> >
> >--- cacca mucca <caccamucca@hotmail.com> wrote:
> >
> > > Network gets blamed all the time because there are
> > > so few skilled network
> > > engineers. We have too many paper CCNPs and CCIEs in
> > > this world.
> > >
> > > Learn how to run a sniffer and sniffer traces and
> > > know the IP packets inside
> > > and out.
> > >
> > > >From: Wes Stevens <wrsteve33-gsccie@yahoo.com>
> > > >Reply-To: Wes Stevens <wrsteve33-gsccie@yahoo.com>
> > > >To: Kirk Graham <kgraham@instructors.net>,
> > > ccielab@groupstudy.com
> > > >Subject: RE: Real world finger pointing at network
> > > >Date: Sun, 7 Aug 2005 08:01:28 -0700 (PDT)
> > > >
> > > >Finger pointing is a way of life where I work.
> > > >Microsoft has so many error messages that can kinda
> > > >point to the network that our server group always
> > > >points to the network first. They don't like it
> > > when I
> > > >get the call because I have more Microsoft
> > > experience
> > > >then they do.
> > > >
> > > >I have seen mtu break some apps run on windows.
> > > They
> > > >sent packets larger then the allowed through a
> > > tunnel
> > > >and the df bit was set. No mtu discovery either. So
> > > >was it a network problem?? Of course, according to
> > > the
> > > >server folks. Of course they don't have a clue what
> > > >the df bit is or mtu discovery.
> > > >
> > > >Wes
> > > >
> > > >--- Kirk Graham <kgraham@instructors.net> wrote:
> > > >
> > > > > Ian has a good suggestion there for
> > > troubleshooting
> > > > > the problem. I would
> > > > > also suspect the new Exchange install over the
> > > > > network.
> > > > >
> > > > > But FYI, for TCP packets Microsoft does set the
> > > DF
> > > > > bit. It should then
> > > > > receive a Fragmentation Needed message with the
> > > > > proper packet size from the
> > > > > router if the packets are too large. As long as
> > > the
> > > > > router's MTU size is
> > > > > properly configured, that shouldn't be a
> > > problem.
> > > > >
> > > > > I have seen a real-world network with an
> > > improperly
> > > > > configured MTU that did
> > > > > cause problems with larger email packets (such
> > > as
> > > > > emails with attachments).
> > > > > The server was sending 4K packets and the router
> > > had
> > > > > a physical 1500 byte
> > > > > MTU, but was misconfigured with a 4K MTU. So the
> > > > > router basically said, "I
> > > > > can't fit 4K packets, send me a 4K packet." We
> > > saw
> > > > > this with a sniffer, and
> > > > > that told us which router was the problem.
> > > Fixing
> > > > > the MTU size corrected
> > > > > the problem.
> > > > >
> > > > > All devices on the same physical network should
> > > > > always agree on MTU.
> > > > >
> > > > > As Ian said, you can do extended pings with DF
> > > bit
> > > > > set, and different MTU
> > > > > sizes to find if there is a problem.
> > > > >
> > > > > Good luck,
> > > > > --kg
> > > > >
> > > > >
> > > > > At 07:40 AM 8/7/2005, Ian Stong wrote:
> > > > > >Have you tested a client locally connected to
> > > the
> > > > > same network as the
> > > > > >servers. If that worked then I would
> > > investigate
> > > > > the microwave link more.
> > > > > >If it doesn't work then it's a Microsuck
> > > problem.
> > > > > >
> > > > > >If it works locally but not over the link the
> > > for
> > > > > your ping tests you should
> > > > > >run extended pings over the link and use
> > > various
> > > > > packet sizes as well as
> > > > > >different data patterns, with the DF bit not
> > > set
> > > > > and then set, etc.
> > > > > >
> > > > > >
> > > > > >
> > > > > >Ian
> > > > > >www.ccie4u.com <http://www.ccie4u.com>
> > > > > >Rack Rentals starting at only $12 and
> > > discounted
> > > > > lab scenarios
> > > > > >
> > > > > >
> > > > > >
> > > > > >-----Original Message-----
> > > > > >From: nobody@groupstudy.com
> > > > > [mailto:nobody@groupstudy.com] On Behalf Of
> > > > > >chon_mon@nym.hush.com
> > > > > >Sent: Sunday, August 07, 2005 5:01 AM
> > > > > >To: ccielab@groupstudy.com
> > > > > >Subject: OT: Real world finger pointing at
> > > network
> > > > > >
> > > > > >I have a simple issue with email. My exchange
> > > 5.5
> > > > > clients and
> > > > > >servers communicate fine over a microwave link
> > > > > (building to
> > > > > >building) without issue. Everyone is happy
> > > with
> > > > > that. Recently,
> > > > > >the exchange server was upgraded to an AD 2003
> > > > > clustered solution,
> > > > > >with updated clients as well. The upgrade did
> > > not
> > > > > go as planned,
> > > > > >and the finger is being pointed at the network
> > > as
> > > > > the problem.
> > > > > >
> > > > > >Typically, I choose to go through the 7 layer
> > > model
> > > > > for
> > > > > >troubleshooting, however I am stuck with people
> > > who
> > > > > believe that
> > > > > >the MTU is the issue across the microwave link.
> > > So
> > > > > now, I am to
> > > > > >SPAN ports on each side to see the traffic
> > > coming
> > > > > and going with
> > > > > >large and small emails sent by the new outlook
> > > > > client.
> > > > > >
> > > > > >I don't see the point to this, because what
> > > > > difference does it make
> > > > > >if its the old clients sending large and small
> > > > > emails, versus the
> > > > > >new test client sending large and small emails
> > > if
> > > > > they all have to
> > > > > >travel the same link between two routers, which
> > > > > don't distinguish
> > > > > >between different versions of Exchange
> > > (assuming,
> > > > > of course, no
> > > > > >access-lists or restrictions on traffic, etc.)?
> > > > > And if MTU was an
> > > > > >issue between buidlings, wouldn't that lead to
> > > > > other problems in
> > > > > >general? Don't Cisco routers fragment packets
> > > by
> > > > > default if they
> > > > > >are too big, and queue them?
> > > > > >
> > > > > >There was a ping test, and it was successful in
> > > > > reachability to the
> > > > > >new clustered AD 2003 exchange IP address from
> > > > > across the microwave
> > > > > >link.
> > > > > >
> > > > > >Now I can understand if packets are being sent
> > > > > across a link with
> > > > > >the DF bit set, and are dropped because they
> > > are
> > > > > larger than the
> > > > > >MTU size. However, I don't think Exchange
> > > sends
> > > > > packets with the
> > > > > >DF bit set.
> > > > > >
> > > > > >Any input on this would be of help.
> > > > > >
> > > > > >
> > > > > >Server<----->Cisco
> > > router<----microwave---->Cisco
> > > > > router<-----
> > >
> >=== message truncated ===
> >
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-- John Matijevic, CCIE #13254 U.S. Installation Group Senior Network Engineer 954-969-7160 ext. 1147 (office) 305-321-6232 (cell)
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