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2 VALNs on same switch port

I have a Catalyst 4506 switch with a single WS-X4013+ sup ll plus and 3- WS-X4548-GB-RJ45V with PoE. I will be connecting Cisco IP Phone 7960. The set up will be the phone will be connected into the wall jack and the PC\Laptop will be connected into the IP Phone. I will be setting up separate VLANs for the phones (VLAN 4) and for the PC\Laptops (VLAN 9) how do I do this when they are plugged into the same switch port? How does it tell which DHCP scope it should pull from?




Re: 2 VALNs on same switch port

Under each interface to which a phone is attached, you'll have something like:

switchport access vlan 9

switchport voice vlan 4

(you may also wish to invesigate AutoQoS too)

You don't say whether you're using the IOS DHCP server on the 4506, or an external DHCP server. Basically, you don't need to do anything with the IOS DHCP server, just create two scopes and the addresses will be allocated from the correct scopes (because the DHCP requests hit the respective VLAN (L3) interfaces as defined on the 4506.

For an external DHCP server, add "ip helper-address " under the VLAN interfaces (you may also wish to disable some other broadcasts which are automatically forwarded when a helper-address is specified), and create the scopes on the server. The DHCP request is modified with a 'giaddr' field to identify the subnet and hence the scope from which an address should be allocated.

In either case, you'll need to configure DHCP Option 150 to point to your CallManager TFTP server(s).

Re: 2 VALNs on same switch port

Thanks. But I am still unclear on how it knows what device it is....a phone or PC? I am using an external server for DHCP.


New Member

Re: 2 VALNs on same switch port

CDP (cisco discovery protocol) automatically places cisco phones in the voice vlan. The DHCP server gives the device an address in the same subnet as the gateway that forwards the request to the server.

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