Some confusion with trunking

Colin Higgins — Sun, 24 May 2009 01:19:59 GMT

Coming from a Cisco background, I find the HP implementation a bit counter-intuitive. It is my understanding that ports set up as trunks (in this case LACP trunks) should be "tagged" for ALL VLANs, including the "default" VLAN1.

But I have seen configurations in which to HP switches are connected and configured with 3 vlans. The default and two others. The client machines (workstations and servers) are assigned to vlans 2 & 3, and the trunk between the switches is tagged for these vlans.

However, the same trunk is not carrying tagged traffic for vlan1 (the default). Example:

vlan 1
name "DEFAULT_VLAN"
untagged B1-B4
ip address dhcp-bootp
no untagged A1-A24
no untagged C1-C24
exit

So here is my question ... If client machines are assigned to vlan 1 on both switches, should the trunk be tagged for these frames? In other words, should the above config look something like this:

vlan 1
name "DEFAULT_VLAN"
untagged B1-B4
ip address dhcp-bootp
no untagged A1-A24
no untagged C1-C24
tagged Trk1
exit

Any info would help greatly!

Re: Some confusion with trunking

JedE — Mon, 25 May 2009 06:27:54 GMT

Colin,

There are three possible options for Trk1:

vlan 1 - send no traffic on VLAN 1
name "DEFAULT_VLAN"
no untagged Trk1

vlan 1 - send untagged traffic on VLAN 1
name "DEFAULT_VLAN"
untagged Trk1

vlan 1 - send tagged traffic on VLAN 1
name "DEFAULT_VLAN"
tagged Trk1

In you case option 2 or option 3 is valid for you client systems and you chose depending on whether you have tagged VLAN 1 traffic on your client system,

Note the LACP trunk port members do not get listed individually in the VLAN tagging configuration.

Jed

topic Some confusion with trunking in Switches, Hubs, and Modems

Some confusion with trunking

Re: Some confusion with trunking