Lacp, dot1q, SPT, native vlan and Management Vlan concepts for

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 couldnt 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 couldnt 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 Wed Nov 04 2009 - 11:15:59 ART