Re: Lacp, dot1q, SPT, native vlan and Management Vlan concepts

I remember working on a Dell Blade server (Dell switch installed) and I
could not bring the trunk up unless I set the native vlan to vlan 1.

On Wed, Nov 4, 2009 at 5:15 AM, Rob Clav <robclav_at_gmail.com> wrote:

> Hi folks,
>
>
>
> I was pretty sure about this concepts in the past, but after check them
> configuring a C2960 with a nortel switch I have several doubts.
>
>
>
> Can you say if i'm wrong with any statement?
>
>
>
> LACP.- standard dynamic protocol used to negociate links aggregation. In
> order to activate it, you need to add a command, to the interfaces
> joinning
> to a virtual interface(layer 2 or not) called port-channel. You can
> activate
> lacp to be the expected(active), to lisen for a lacp negotiation from the
> other site or to say the channel-group is on without negociation. At
> port-channel virtual interface you need to configure the same that you
> configure at physical int.
>
>
>
> DOT1Q and native vlan.- standard dynamic protocol in order to allow more
> than one vlan crossing the link. One of these vlans is called native
> because
> is the one used to carry the control protocols like cdp,spt(one instance)
> and so one. This one is send it untagged by default. The rest of the vlans
> are send tagged. You can tag native vlan in some devices like 3750 but at
> 2960 you couldn t with the command "vlan dot1q native tag". The kind of
> encapsulation should be choosed in some models supporting isl. Then you can
> say if the trunk will be desirable, will expect the action of the other
> site
> of the link, if will be on or the negotiation will be deactivated.
>
>
>
> Management VLAN.- Is used at layer 2 devices to configure an IP Address in
> order to manage the switch. This one could be the native vlan or not. By
> default at layer 2 devices, this one must be the native as well.
>
>
>
> SPT.- Well-known anti layer 2 loop protocol. There are several kinds like
> CST, PVST, PVST+(cisco) ,RST, MST, RPVST+(cisco). The first one support
> only
> one instance for whole spt domain, and the rest support a instance and then
> a root for each vlan.
>
> As compatible SPT I use, CST, or mst. I read at some forums that 802.1q
> doesn't support PVST+ except if you use only Cisco switches.
>
>
>
>
>
> Summary,
>
> I have a Cisco 2960 trying to establish an etherchannel with a 801.q trunk
> configuration. But it doesn't works. Obviously, I tried to break the
> problem
> in some smaller ones. Well the main problem is that I need to change the
> management vlan to other(Vlan 63) because the subnetting. And then I tried
> to make the management(Vlan 63) as a native also. I tried too, using one
> vlan(63) for management and other one(Vlan 1) as a native. But no positive
> results.
>
>
>
> The picture of the config is that I have vlan 63 as management and I assume
> vlan 1 is the native, because you couldn t remove it.
>
>
>
> 1.-I tried to check connectivity between one link without trunk or
> etherchannel config, basically acting as an access port. It works
>
> 2.-I tried to configure a trunk between them, and didn't work. In fact, I
> tried several configuration, negotiating the trunk and forcing it, but
> nothing.
>
> 3.-LACP seems to work fine, without 802.1q.
>
>
>
> Well at the end of this email I realize that I have a problem with the
> trunk+native vlan and SPT, but I don't know why. It's a lab environment so
> I'm sure there's no third cable between them to loop it. Any idea?
>
> Thanks in advance,
>
> Robclav
>
>
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Received on Thu Nov 05 2009 - 09:52:12 ART