LACP, Dot1Q, native vlan and MGT vlan

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.

RobClav