From: Deep Ratan (deep.ratan@gmail.com)
Date: Fri Sep 30 2005 - 12:56:07 GMT-3
John, THANK YOU! My question is now fully answered.
On 9/30/05, Sheahan, John <John.Sheahan@priceline.com> wrote:
>
> If you do a "sh mac-address-table" you will only see the local port that
> shows how the switch gets to any particular mac address. For instance, in
> the following example, mac-address 0800.20c5.888f is on VLAN 303, but does
> not reside on the local switch. The local switch does tell you that you
have
> to cross Port Channel 30 to get to it (Po30). This mac might not even be on
> the next switch, it could on another switch connected to that switch with a
> trunk. You would have to do a "sh mac-address-table address
> 0800.20c5.888f" to find out how the next switch knows about that mac
> address and follow it until you get to the last switch which will
eventually
> show you a locally connected port.
>
> * 303 0800.20c5.888f dynamic Yes 35 Po30
>
> -------------------------example from a switch running
> IOS---------------------------------------
>
> 6500-01>sh mac-address-table
>
> Legend: * - primary entry
>
> age - seconds since last seen
>
> n/a - not available
>
> vlan mac address type learn age ports
>
>
>
------+----------------+--------+-----+----------+--------------------------
>
> * 303 0800.20d9.27b4 dynamic Yes 0 Gi4/14
>
> * 303 0800.20f1.21ad dynamic Yes 0 Gi4/22
>
> * 309 0009.b789.9008 dynamic Yes 5 Gi4/7
>
> * 308 0002.ba47.f7ff dynamic Yes 25 Gi4/4
>
> * 308 0080.8c01.e2bc dynamic Yes 150 Gi7/7
>
> * 303 0800.20c5.888f dynamic Yes 35 Po30
>
> * 308 0090.27f9.6dbb dynamic Yes 290 Po30
>
> * 309 0009.b789.90d5 dynamic Yes 5 Po30
>
> * 303 0003.ba08.e68e dynamic Yes 0 Gi4/24
>
> * 304 0003.ba08.e68e dynamic Yes 0 Gi4/25
>
> * 303 0014.3850.928a dynamic Yes 5 Gi7/9
>
> * 303 0003.ba09.90a9 dynamic Yes 35 Po30
>
> ------------------------------
>
> *From:* Deep Ratan [mailto:deep.ratan@gmail.com]
> *Sent:* Friday, September 30, 2005 11:26 AM
> *To:* Sheahan, John
> *Cc:* ccielab@groupstudy.com
> *Subject:* Re: layer-2 interview question
>
> John,
> Your reply answers my question. I didn't know layer-2 information is
> propagated via VTP across the entire VLAN domain.
>
> In reiteration: If I do a "show cam dyn" on a switch, I'll see the mac
> address of an end user machine that is connected 10 switches away, assuming
> both switches have the same VLAN, VTP is working, etc?
>
> On 9/30/05, *Sheahan, John* <John.Sheahan@priceline.com > wrote:
>
> "sh cam dyn" will show you all mac addresses that the switch knows about
> from a layer two persective. That includes machines plugged into hubs
> that are plugged into switch. It will also know about mac addresses on
> other switches that are trunked to the switch.
>
> If you are running IOS, you can easily sort through 10,000 mac addresses
> with the following command:
>
> "sh mac-address-table | begin 0009.b7e0.c2e"
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto: nobody@groupstudy.com] On Behalf Of
> Deep Ratan
> Sent: Friday, September 30, 2005 11:04 AM
> To: ccielab@groupstudy.com
> Subject: Re: layer-2 interview question
>
> does "show cam" display mac address of A) machines directly connected to
> the
> switch ports of the switch or B) machines on all vlans across all
> switches
> in those vlans?
>
> If B) is true, the output of that command could have 10,000 entries.
>
> On 9/30/05, Adam S. Roth <adam@therothfamily.net> wrote:
> >
> > Show cam
> >
> > This email message and any attachments are intended for the use of the
> > addressee(s) indicated above. Information that is privileged or
> otherwise
> > confidential may be contained herein. If you are not the intended
> > recipient(s), you are hereby notified that any dissemination, review,
> or
> > use
> > of this message, documents, or information contained herein is
> strictly
> > prohibited.
> >
> >
> >
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> > Deep
> > Ratan
> > Sent: Friday, September 30, 2005 10:48 AM
> > To: ccielab@groupstudy.com
> > Subject: layer-2 interview question
> >
> >
> > Hi Everyone,
> > Sorry to ask a networking-101 question but being a WAN guy, I haven't
> been
> > working with switches in the past few years. An interviewer asked me
> this
> > question, "If I give you a MAC address that is causing a broadcast
> storm,
> > how will you locate the culprit in a switched environment that has
> several
> > dozen switches and routers?"
> >
> > I replied, "You'll need to give me a layer-3 address so I can trace it
> to
> > the right switch/router and then look up the ARP table to see on what
> port
> > the offending machine lives" The interviewer didn't like the answer.
> In
> > retrospect, I should probably have said, "A broadcast storm renders
> the
> > network unusable, so I'll start with looking at my network management
> > station to see what LAN segment is giving off a critical alarm"
> >
> > Anyway, my question to members of groupstudy is this: In an
> environment
> > with
> > several dozen switches, if you're given just a MAC address, can you
> find
> > out
> > where the machine lives?
> >
> > thanks, Deep
> >
> >
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