From: Jonathan V Hays (jhays@jtan.com)
Date: Wed Jul 02 2003 - 18:11:45 GMT-3
No I didn't try that command.
Darn it, Mas - you're making more work for me. <G> Now I have to look up
'debug dtp' on CCO...
Thanks a bunch,
Jonathan
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> Behalf Of P729
> Sent: Wednesday, July 02, 2003 2:36 PM
> To: Jonathan V Hays; ccielab@groupstudy.com
> Subject: Re: bridging removes port from 3550 vlan - FIXED
>
>
> Sage advice.
>
> Every trunking-capable Catalyst and ProCurve switch I've run
> across will, by
> default, form a trunk (and EtherChannel) if asked to.
>
> Just curious, did you also try 'debug dtp' ?
>
> Regards,
>
> Mas Kato
> https://ecardfile.com/id/mkato
>
> ----- Original Message -----
> From: "Jonathan V Hays" <jhays@jtan.com>
> To: <ccielab@groupstudy.com>
> Sent: Wednesday, July 02, 2003 11:01 AM
> Subject: RE: bridging removes port from 3550 vlan - FIXED
>
>
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> > Behalf Of Jonathan V Hays
> > Sent: Monday, June 30, 2003 12:35 PM
> > To: ccielab@groupstudy.com
> > Subject: bridging removes port from 3550 vlan
> >
> > My lab study partner has a pair of catalyst 3550s running the
> > latest EMI
> > image, (C3550-I5Q3L2-M), Version 12.1(13)EA1a.
> >
> > Whenever we configure DLSW (or simple bridging) the
> fastethernet 3550
> > switch ports connected to the DLSW-enabled routers are
> > removed from the
> > configured VLAN. You can execute "show vlan" on the switch
> > and the DLSW
> > ports are missing. Removing the DLSW configuration from the router
> > restores the port to the VLAN. It goes without saying, but
> I'll say it
> > anyway, we have tried various ports and rebooted switches
> and routers
> > but that does nothing to fix this problem.
> >
> > The Cisco Bug Toolkit did not give me any hits on this problem.
> >
> > Does anyone have any ideas on this one?
> >
> > Thanks,
> >
> > Jonathan
> > ______________________________________________________________
>
>
> Thanks to everyone for their suggestions. The problem is FIXED.
>
> I'm somewhat embarrassed to report the details. The fault was ours for
> ignoring the details of the Catalyst 3550 Configuration Guide.
>
> I post this in the hopes that others don't make this same
> mistake and to
> remind people that part of being a Groupstudy member is the
> responsibility to GIVE BACK and not just to beg for information and
> fixes on our own problems.
>
> My lab partner and I spent some time focusing on this problem
> yesterday
> and fixed it, although we still do not fully understand the mechanism
> involved.
>
> We had been in the habit of taking a shortcut to assign a
> Catalyst 3550
> port to a VLAN by simply typing "switchport access vlan vlan-id". In
> most cases the switch and the attached routers in our lab functioned
> just fine. However, when DLSW is configured and an ethernet port
> connected to the 3550 is configured with "bridge-group 1" then the
> switch will quit access mode and start TRUNKING on those ports, as
> verified by debug and "show int".
>
> The solution is to configure each port with the command
> "switchport mode
> access" as recommended in the configuration guide. Without
> that command
> the port is not locked into access mode.
>
> I was wrong that about bridging. Configuring bridging alone on the
> router port did not force the switch to start trunking on the
> connected
> port. It is only when you configure DLSW that it starts doing
> this. Why
> this is I still have no clue.
>
> We used "sh interface" and various flavors of "debug spanning-tree" to
> track down this problem.
>
> It is interesting that these new-fangled switches <G> will trunk on a
> port automatically. For example, if you just plug a crossover cable
> between any two ports on two 3550s they will start trunking.
>
> A bit of repetition should hammer this into the brains of those of us
> unfamiliar with the 3550.
>
> When you configure a 3550 port for a vlan do it like this:
>
> switchport mode access
> switchport access vlan 13
>
> You leave off the first command at your peril!
>
> Jonathan
>
>
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