DHCP broadcasts not going over VTP trunk.

The scenerio is like this.

Switch A --> CORE (4006) ---> Switch B

A and B are Cisco 2524 and the core is a 4006. The 4006 is VTP server, A and B are vtp clients. VTP information is propagating perfectly.

Vlan 103 has been setup on the core switch and has been asigned to ports on A and B. The user is on switch A and his resources are on switch B.

Switch B has vlan 103 assigned to a port with a hub attached. The hub is another network that contains the resources the user needs. DHCP, Internet etc.

Trunking has been configured between A to Core and B to Core.

When the user plugs into vlan 103 on switch A, he does not get DHCP from the hub on switch B.

If I configure another port on switch B has vlan 103 and plug into it, I get DHCP from the other network like I'm supposed to.

My question is why isn't the hub's broadcasts making it over to the user on switch A?

What should I look at?

Thanks for any help you can offer.

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Also, the link from switch B to the Core is a gigabit Eth over fiber. The port is on the Router Switch Card. I learned that GMRP was enabled for that blade so I turned it off.

snipped-for-privacy@yahoo.com wrote:

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One command: IP helper-address x.x.x.x , where x.x.x.x is your DHCP server. This needs to be done on each vlan interface, since by default VLAN's don't forward broadcasts between each other.

Take a look this:

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snipped-for-privacy@yahoo.com wrote:

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Actually, that's not it. I'm not concerned at all with IP at them moment. I just want one big broadcast domain that spans from switch A to Core to switch B.

I think the problem is that one of the vtp trunks is coming in on a router switch module. They router blade is sort of out there on its own and I'm not sure how to get it to share in the VLAN fun.

Basically the RSM has 2 gig E ports that are connected to the switch backplane via a bridge group.

When I activate the vlan on any of my trunk ports STP has a shit fit and shuts down the port.

I'm wondering if this is because of the bridge and what I should do about it. Should I etherchannel them? Turn off STP?

Is it something else?

resp> One command: IP helper-address x.x.x.x , where x.x.x.x is your DHCP

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I think you don't have a good picture of how things are connected together . Don't turn off spanning tree whatever you do . The ports are shutting down because somehow you have created a loop in your network and it is protecting that . If it was as simple as your drawing would suggest there is no reason it should not work . I think somewhere something is getting missed on how it is all connected . If the connecting links are trunks check to make sure those trunks are being allowed on both sides of the trunk, on the 4006 and on the 2500's . Just because the vlan is being propagated doesn't mean it is allowed across those links on either side , they may be manually pruned off.

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