From: ccie2be (ccie2be@nyc.rr.com)
Date: Fri Dec 10 2004 - 12:04:30 GMT-3
Good point.
But, isn't the "management" vlan is also used to carry vtp and stp bdpu's
packets or is that always vlan 1?
Also, can the "default" vlan be changed? If so, how?
TIA, Tim
----- Original Message -----
From: "Brian McGahan" <bmcgahan@internetworkexpert.com>
To: "Lee Donald" <Lee.Donald@t-systems.co.uk>; <ccielab@groupstudy.com>
Sent: Friday, December 10, 2004 9:39 AM
Subject: RE: 3550 - Default Vlan - Native Vlan & Trunks
> The "default" VLAN on the 3550 simply means the VLAN that access
> switchports are assigned to automatically when the command "switchport
> access vlan" is not manually configured. Don't confuse this with the
> term "management vlan" used on layer 2 platforms.
>
> Layer 2 switches use the "management vlan" to refer to the VLAN
> that the switch has an IP address configured in. Most layer 2 platforms
> only allow you to have one layer 3 address in exactly one VLAN. With
> the 3550 however, this is not the case since it's a layer 3 switch. Any
> SVI or native routed interface is technically a "management" interface,
> because you can telnet to them, send SNMP GETs to them, etc.
>
>
> HTH,
>
> Brian McGahan, CCIE #8593
> bmcgahan@internetworkexpert.com
>
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
> Toll Free: 877-224-8987 x 705
> Outside US: 775-826-4344 x 705
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>
>
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> > Lee Donald
> > Sent: Friday, December 10, 2004 2:56 AM
> > To: Brian McGahan; ccie2be; Keane, James; ccielab@groupstudy.com
> > Subject: RE: 3550 - Default Vlan - Native Vlan & Trunks
> >
> > The management vlan can be changed, and Cisco encourage you to do so.
> >
> > It is a good idea to change the default vlan 1, because of security. A
> new
> > switch could over write your vlan info when brought up etc.
> >
> >
> >
> > -----Original Message-----
> > From: Brian McGahan [mailto:bmcgahan@internetworkexpert.com]
> > Sent: 09 December 2004 22:37
> > To: ccie2be; Keane, James; ccielab@groupstudy.com
> > Subject: RE: 3550 - Default Vlan - Native Vlan & Trunks
> >
> > > Now, the default vlan. This, by default, is vlan 1 and I don't
> think
> > you
> > > can change that. This is the vlan over which the vtp and stp
> messages
> > > travel. And, from what I understand, even when this vlan isn't
> > allowed
> > > over
> > > a trunk, the vtp and stp traffic still goes over the trunk. Only the
> > user
> > > data from vlan 1 doesn't go over the trunk.
> >
> > Correct. This is known as "VLAN 1 Minimization". When VLAN 1 is
> > removed from a trunk link, only normal user traffic in VLAN 1 is
> > removed. Necessary network traffic such as VTP and STP BPDUs still
> use
> > VLAN 1 for transmission between connected neighbors.
> >
> >
> >
> > Brian McGahan, CCIE #8593
> > bmcgahan@internetworkexpert.com
> >
> > Internetwork Expert, Inc.
> > http://www.InternetworkExpert.com
> > Toll Free: 877-224-8987 x 705
> > Outside US: 775-826-4344 x 705
> > 24/7 Support: http://forum.internetworkexpert.com
> > Live Chat: http://www.internetworkexpert.com/chat/
> >
> >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> > Of
> > > ccie2be
> > > Sent: Thursday, December 09, 2004 3:42 PM
> > > To: Keane, James; ccielab@groupstudy.com
> > > Subject: Re: 3550 - Default Vlan - Native Vlan & Trunks
> > >
> > > James,
> > >
> > > I think the issue you raise is the cause of great confusion to many
> > > people.
> > > But, the issue I think is one primarily of terminology.
> > >
> > > the native and default vlan's refer to different unrelated vlan's
> and
> > have
> > > different purposes for existing.
> > >
> > > The native vlan is only relevant to 802.1q trunks and has nothing to
> > do
> > > with
> > > anything else. As you probably know, a packet crossing a 802.1q
> trunk
> > > will
> > > have a vlan tag or it won't. If the packet doesn't have a vlan tag,
> > how
> > > does the switch know what to do with the packet? The answer is the
> > switch
> > > assume the packet is part of the native vlan and switches the packet
> > > accordingly. Which vlan is the native vlan? Whichever vlan YOU
> make
> > the
> > > native vlan. If you don't explicitly make any vlan the native vlan,
> > the
> > > default vlan is the native vlan.
> > >
> > > Now, the default vlan. This, by default, is vlan 1 and I don't
> think
> > you
> > > can change that. This is the vlan over which the vtp and stp
> messages
> > > travel. And, from what I understand, even when this vlan isn't
> > allowed
> > > over
> > > a trunk, the vtp and stp traffic still goes over the trunk. Only the
> > user
> > > data from vlan 1 doesn't go over the trunk.
> > >
> > > If I'm wrong with anything I've said, hopefully, someone will let us
> > know.
> > >
> > > HTH, Tim
> > >
> > >
> > > ----- Original Message -----
> > > From: "Keane, James" <James.Keane@agriculture.gov.ie>
> > > To: <ccielab@groupstudy.com>
> > > Sent: Thursday, December 09, 2004 11:11 AM
> > > Subject: 3550 - Default Vlan - Native Vlan & Trunks
> > >
> > >
> > > > I was asked a fairly straightforward question yesterday
> > > >
> > > > quote
> > > >
> > > > 'let's say you are only allowed to send odd
> > > > VLANs, 3,5,7,9,11, over a trunk, how about the default VLAN ? I
> > think
> > > you
> > > cannot disallow the default VLAN 1 unless you set the native VLAN to
> > > > something else, is that right ?'
> > > >
> > > > unquote
> > > >
> > > > I responded with sure you cant disable the vlan you are trunking
> on
> > ..
> > > but
> > > I'll just verify that in the lab...
> > > >
> > > >
> > > > To my astonishment I was able to completely remove vlan 1 from the
> > trunk
> > > while keeping my native vlan as 1..
> > > >
> > > > now the trunk mode on one side reads 'n-802.1q' and '802.1q' on
> the
> > > other.
> > > Not quite sure what the n-802.1q is all about ??!
> > > >
> > > > What is going on ?
> > > >
> > > > One more final thing is buggin me - the default vlan is one and
> the
> > > native
> > > vlan is one - you can change the native ...
> > > >
> > > > ... can you change the default ???
> > > >
> > > >
> > > >
> > > > I thought I understood this topic (grrrr)
> > > >
> > > >
> > > > Any light on this would be greatly appreciated
> > > >
> > > >
> > > > I am going back to practical studies II to revise the basics !!!
> > > >
> > > >
> > > > Regards,
> > > >
> > > > James Keane
> > > >
> > > >
> > > >
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