From: Wei Yang (weikyang@ms3.hinet.net)
Date: Wed Jul 02 2003 - 23:14:03 GMT-3
i have some points here related to the 3550 switch that needs more
clarification, and i'll be thankful if anybody can enlighten me on the
following:
1. if the 3550 comes without any configuration, it has routing disabled and
therefore, functions as a pure layer 2 switch?
2. if this is the case, while attaching clients to the 3550 for dlsw
bridging on one site does not need the statement 'bridge-group 1' on the
client's interface(since it will still be able to forward nonroutable
protocols to the router).
3. only when 2 vlans or more are created and ip routing is enabled on the
3550 should one consider adding the 'bridge-group 1' statement on the vlan
interface for dlsw+ bridging since on the virtual layer 3 interface(the vlan
interface with ip address configured) it will not be routing nonroutable
protocols such as netbeui.
4. by default, the switchports on the 3550 will autosense whether a port is
a trunk port or an access port(in this order), unless otherwise configured.
please advise if i missed anything. thanks in advance!
wei
----- Original Message -----
From: "P729" <p729@cox.net>
To: "Jonathan V Hays" <jhays@jtan.com>; <ccielab@groupstudy.com>
Sent: Thursday, July 03, 2003 9:12 AM
Subject: Re: bridging removes port from 3550 vlan - FIXED
> hehe--there always seems to be one more debug command...for something!
>
> DTP stands for Dynamic Trunking Protocol. Perhaps debugging it might give
up
> clues as to what the switch is seeing that makes it form the trunk.
>
> Regards,
>
> Mas Kato
> https://ecardfile.com/id/mkato
>
> ----- Original Message -----
> From: "Jonathan V Hays" <jhays@jtan.com>
> To: "'P729'" <p729@cox.net>; <ccielab@groupstudy.com>
> Sent: Wednesday, July 02, 2003 2:11 PM
> Subject: RE: bridging removes port from 3550 vlan - FIXED
>
>
> 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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> >
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