From: Chris Larson (clarson52@comcast.net)
Date: Sat Nov 20 2004 - 02:30:08 GMT-3
No, my understanding is that VTP, cdp and DTP are always carried over vlan
1.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ccie2be
Sent: Friday, November 19, 2004 12:19 PM
To: Bob Sinclair; jfaure@sztele.com; ccielab@groupstudy.com
Subject: Re: Another Catalyst 802.1q trunking issue
Bob,
I hope this isn't a dumb question but...
By default, vlan 1 is the native vlan and the management vlan ie it carries
all that vtp, cdp and DTP stuff. When the native vlan is changed to
something other than vlan 1, does that mean that the management vlan is also
changed and all that management traffic is now carried in the new native
vlan?
Thanks, Tim
----- Original Message -----
From: "Bob Sinclair" <bsin@cox.net>
To: <jfaure@sztele.com>; <ccielab@groupstudy.com>
Sent: Saturday, November 29, 2003 7:50 PM
Subject: Re: Catalyst 802.1q trunking issues
> Juan,
>
> I put a sniffer on a 3550 dot1q trunk and observed the following when I
> removed Vlan 1 from the dot1q trunk, but left it as the native vlan:
>
> 1. All traffic leaving the port is tagged
> 2. VTP, CDP and DTP traffic leave the port with Vlan 1 tags
> 3. No other Vlan 1 traffic is seen leaving the port (including no Vlan 1
> BPDUs)
> 4. All BPDUs are PVST+ encapsulated, to address 01-00-0c-cc-cc-cd
>
> This should not cause a problem as long as all of your switches are Cisco
> and similarly configured:
> a. The Cisco switches recognize that CDP, VTP and DTP are not to be
> forwarded
> b. The Cisco switches recognize the encapsulated BPDUs
>
> You very well might have an STP issue if you connect such a port to a
> non-Cisco switch, because the brand X switch will not see any recognizable
> BPDUs, and the Cisco switch may not recognize the untagged BPDUs on the
> native vlan coming from the Brand X switch. It would seem prudent to
allow
> the native vlan across the trunk.
>
> But then, you would never put a Brand X switch in your network...
>
> would you?
>
> -Bob Sinclair
> CCIE #10427, CISSP, MCSE
> bsinclair@netmasterclass.net
>
>
> ----- Original Message -----
> From: <jfaure@sztele.com>
> To: <ccielab@groupstudy.com>
> Sent: Saturday, November 29, 2003 12:55 PM
> Subject: Catalyst 802.1q trunking issues
>
>
> > Hi all:
> >
> > -From the 6500 CCO configuration guide, about removing vlan1 from the
> > trunk:
> >
> > "You can remove VLAN 1. If you remove VLAN 1 from a trunk, the trunk
> > interface continues to send and receive management traffic, for example,
> > Cisco Discovery Protocol (CDP), VLAN Trunking Protocol (VTP), Port
> > Aggregation Protocol (PAgP), and DTP in VLAN 1. "
> >
> > -But also, in the same document:
> >
> > "Disabling spanning tree on the native VLAN of an 802.1Q trunk without
> > disabling spanning tree on every VLAN in the network can cause spanning
> > tree loops. We recommend that you leave spanning tree enabled on the
> native
> > VLAN of an 802.1Q trunk. If this is not possible, disable spanning tree
on
> > every VLAN in the network. Make sure your network is free of physical
> loops
> > before disabling spanning tree"
> >
> > And then my question is:
> > If you have several dot1q trunks configured in your swiched network in
> such
> > a way that these trunks don't allow pass the vlan1, the vlan1 is the
> native
> > vlan for them (you can see this doing a "sh int trunk") and the
interface
> > vlan 1 is in shutdown state in all the switches (but no STP disabled on
> > this vlan 1), can you have any stp issues like to be unable to block
some
> > loops?
> > What happens with the STP control traffic if vlan 1 isn't included on
the
> > trunks? Having vlan 1 in shutdown state maybe interpreted by the system
as
> > it has stp disabled for this vlan? I'm usign RAPID PVSTP
> >
> > Any thoughs will be greatly apreciated.
> >
> >
> >
> >
> >
> > Juan Faure Ferrer
> > email: jfaure@sztele.com
> >
> > Lmnea de Negocio de Telematica y CC
> > Ingeniero de Integracisn de Redes y Sistemas
>
> --------------------------------------------------------------------------
> --
> >
> > SOLUZIONA TELECOMUNICACIONES
> > Servicios Profesionales de UNION FENOSA
> > Jerez, 3
> > 28016 MADRID
> > tel 91 579 30 00 fax 91 350 72 83
>
> --------------------------------------------------------------------------
> -
> >
> > _______________________________________________________________________
> > Please help support GroupStudy by purchasing your study materials from:
> > http://shop.groupstudy.com
> >
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
>
> _______________________________________________________________________
> Please help support GroupStudy by purchasing your study materials from:
> http://shop.groupstudy.com
>
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Thu Dec 02 2004 - 06:57:47 GMT-3