Ah gee, Leigh Anne, even a Linux server takes more than five minutes to
shutdown, move, and reboot :->
Interesting point about experienced folks who really don't understand the
wire, but need to. I once interviewed with a company that wanted people with
extensive sniffer experience because apparently every time there was any
kind of a problem on any of their 1000+ host segments, their engineers broke
out the sniffers, determined the precise source of the exact and particular
problem, and corrected it. Maybe that meant replacing a NIC that was putting
out "excessive" traffic. Maybe that meant fine tuning filtering in one place
or another. Talk about not being able to see the forest because of the
trees. But doing a network redesign just wasn't "in the works"
One nice thing I find being on the sales engineer side - lots of folks
actually at least pretend to listen to me. Something that was not
necessarily true when I was a technology manager. :->
chuck
-----Original Message-----
From: Leigh Anne Chisholm [mailto:[EMAIL PROTECTED]]
Sent: Friday, July 07, 2000 10:34 AM
To: Chuck Larrieu; [EMAIL PROTECTED]
Subject: RE: Fw: Easy Brain Teaser (Switching)
Well actually Chuck, as I posted in my message, many people set up a server
in one room, and then move it to another. I recently was at a site where
such a thing happened - they haven't been pleased with their Catalyst 5500
being "buggy" and have tried everything to correct the network connectivity
problem, INCLUDING upgrading to the latest IOS. They've been less than
pleased Cisco customers. John Neiberger probably posted the "teaser"
question as a learning experience for others on the list, because it's
something he's had to find out the hard way as well.
As an aside, but related - the question has often arisen: "Would you hire
someone with 2 years of experience, or a newly certified
CCNA/CCDA/CCNP/CCDP". My answer would be (visualizing Howard B here for a
moment...) "It depends". (-:
There are many people in the field, like the administrator at the
organization I reference above, who have been working in the IT field for
years, who do their job well, but many "experienced administrators" haven't
understood how the devices operate. And often, these same individuals don't
have the capability to really optimize performance on their networks as a
result. Another organization comes to mind where there were 2000 stations,
each running TCP/IP, NetBEUI, and IPX (3 frame types), some stations ran
AppleTalk, and others various proprietary protocols as required. This was a
completely bridged environment - no routers. Workstations used broadcasts
to find servers - each Windows for Workgroups PC having file and print
sharing enabled. No one had any idea how to monitor what was happening on
the wire, or the impact of their configurations. They knew the network was
slow... A little education has done WONDERS for resolving their issues!
Now someone who has had training, who really understands the fundamentals of
how things operate can run circles around the "experienced" but "uneducated"
network administrator. The issue John brought to this list is a perfect
example. In training circles, it's known that a typical user will only use
30% of a product's functionality without training--and that makes for a
pretty expensive product. But that's why most of us are part of this
group - to go beyond the 30% rule.
-- Leigh Anne
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
> Chuck Larrieu
> Sent: Friday, July 07, 2000 6:56 AM
> To: [EMAIL PROTECTED]
> Subject: RE: Fw: Easy Brain Teaser (Switching)
>
>
>
> Realistically, how much time does it take to move a department? Some folks
> do things like this evenings or weekends. By the time the movees
> get back to
> work, the CAM table is no longer an issue.
>
> Chuck
>
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
> Jorge Rodriguez
> Sent: Thursday, July 06, 2000 1:13 PM
> To: [EMAIL PROTECTED]; Roberta J. Flinn
> Cc: Jay Cann; Michael Burgess
> Subject: RE: Fw: Easy Brain Teaser (Switching)
>
> This is a very interesting issue that must have a work around,
> specially when moving workstation/servers to other locations.
> Sure, one server is ok, what about moving a whole department
> from one Cat5000 to another ? or if you schedule Station moves
> on a weekly basis ? Do you want to clear cam all the time ?
> I don't think so !-:) Maybe Cisco has some answers to these type of
> scenarios.
>
> In the server scenario I would instead of "Clear cam dyn ", issue
> a "clear cam Mac_Address Vlan#"" for that server if is going to a
> different
> port on the same switch, this way the switch will not have to rebuild the
> MAC table.
>
>
>
> ------Original Message------
> From: "Roberta J. Flinn" <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]
> Sent: July 6, 2000 6:43:42 PM GMT
> Subject: Fw: Easy Brain Teaser (Switching)
>
>
>
>
> This has to do with the learning (cam table) in the switch. The
> entries are
> set to age out of that table after a preset number of minutes. Until the
> older entry "ages out" the switch will see the same MAC address on two
> different ports. It cannot make a switching decision so it does
> not send to
> either port. To solve this issue - you can issue a "clear cam dynamic"
> command. This will flush the CAM table and force the switch to rebuild it
> with the correct information. (Note: can cause additional traffic
> for a few
> moments because the switch will flood packets destined for unknown MAC
> addresses out all ports except the one from which it received the packet.)
>
> Roberta J. Flinn
> CCDP, CCNA, MCNE, MCSE
>
> ----- Original Message -----
> From: "John Neiberger" <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Thursday, July 06, 2000 8:04 AM
> Subject: Easy Brain Teaser (Switching)
>
>
> > Here's an easy one, because I'm nicer than Chuck. :-) Even though it's
> > easy, it's still practical. And for those of you who
> immediately know the
> > answer, let the less experienced people mull this one over for a bit.
> >
> > You have a Catalyst 5000 with several servers connected and
> you've decided
> > to rearrange the port assignments. You disconnect one server in
> > particular
> > > and move it to another port, then quickly discover that it now has no
> > > network connectivity. You attempt to access the network for
> a couple of
> > > minutes to no avail. In supreme frustration, you head to the
> break room
> > for
> > > coffee and donuts.
> > >
> > > When you come back several minutes later you find that the server now
> has
> > > network connectivity and all is well, no problems.
> > >
> > > What is the most likely cause of this behavior and what could you have
> > done
> > > to remedy the situation immediately?
> > >
> > > Good luck!
> > >
> > > John
> > >
> > >
> > >
> > >
> > >
> > > _______________________________________________________
> > > Say Bye to Slow Internet!
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> > >
> > > ___________________________________
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> > >
> >
>
> ___________________________________
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>
> Jorge Rodriguez /CCNA
> Network Analyst
> R&S Networks Inc
> 1112 Boylston Street
> Suite 222
> Boston, MA 02115
> 1-781-614-1294
> http://www.netwire.n3.net/
> http://www.learncisco.n3.net/
>
> ........................................................
> iWon.com http://www.iwon.com why wouldn't you?
> ........................................................
>
> ___________________________________
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