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New Member

vlan trunking question...

here's my layout.

i have an alcatel switch as the core. i have 2 vlans and

i have a 3524 directly connected to a port on the alcatel using vlan 3. so when i connect to this switch i get an address in the range. that all works fine.

now, i have another 3524 connected to the first 3524 using a gigastack gbic. i would like all of these ports to be in vlan 4

so i have configured the ports between the alcatel and the first 3524 as dot1q trunks. i also have the ports between the two 3524's as dot1q trunks. the first 3524 has ports configured as access vlan 3 and that works fine. on the second 3524 i have all ports configured as access vlan 4 (except for the uplink which is a trunk). i cannot get pull an address in the range though.

what i am doing wrong? i am just getting started with vlans.



Re: vlan trunking question...

On the alcatel trunk port, make sure both VLANs 3 and 4 are being trunked.

Same thing on 3524 port connecting to alcatel. Make sure the native vlan on the trunk is vlan 3. Alcatel may call this native, untagged, or something else. The native VLAN in 802.1q is just a untagged VLAN.

On the alcatel make sure there ports in VLAN 4. If the Alcatel is acting as a L3 router then make sure it is routing for VLAN 4 and if there is no DHCP server in VLAN 4 that it is forwarding/relaying DHCP requests to a server.

For the 3524 to 3524 trunk, similar thing. Make sure the trunk is carrying both VLANs 3 and 4 and that the native VLAN is the same. You can do a "show int g0/1 switchport' for example to see trunk information for that port.

Spanning tree may also be a issue. Make sure that vlan 4 isn't being blocked on the trunk between the 3524 and alcatel as alcatel may not like PVST (I'm not familiar with alcatel).

HTH, Erick

New Member

Re: vlan trunking question...

i do have a dhcp server in vlan 2 ( i have dhcp relay setup on the alcatel and it's working. i also have routing setup. vlan 4 does work if i connect it straight to the core alcatel.

i am not sure if i have vlan 4 associated with the alcatel port though. i know that port is in vlan 3, but i am not sure about 4. that may be my problem.

thanks for your recommendations. hopefully your suggestions will provide a resolution for me.


Re: vlan trunking question...

Yea, the alcatel port has to be configured to trunk both vlans 3 and 4 with 3 being untagged/native. couldn't find docs publicly available for alcatel but you should be able to find a show command relating to trunking to tell you whats going on.

New Member

Re: vlan trunking question...

that was the problem. i didn't have vlan 3 trunked on that port. i had all other vlans but i was missing that one.

thanks! i knew i was overlooking something simple.

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