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New Member

dhcp using cat 3550 EMi

I have 3 catalyst 3550 in access layer. each catalyst is connecting through a fiber to the core catalyst 4507 using trunking. The servers are in separate VLAN than the users. how do I assing Ip address to each user in different vlan.

can I create vlan interface on the cat3550 and use Ip helper address command ?

Or should I put the servers in the same vlan as the users?

I would like to keep all the servers in one separate VLAN.

New Member

Re: dhcp using cat 3550 EMi

HI there

Keeping the servers separate from the users is the right thing to do. Try the following:

1. Work out a plan of how many VLANs you want to have. You might want to have one VLAN per department in your office.

2. Make sure that you have a router (at least one) in your network that's capable of doing VLAN routing. This router can be a routing module on the 4507 or on the 3550 EMI. Trunk all the links that inter-connect the switches.

3. Create sub-interfaces on the router(s) and also create VLANs on the switches.

4. Setup a DHCP server on your network (you should already have one). Setup DHCP scopes on this DHCP server for each VLAN.

5. Assign the command "ip helper-address" on each of the sub-interface that points to the DHCP server.

That should be all that you have to do. You might want to do some reading prior to carry out the stuff I mentioned above. Just go to cisco web site and search for VLAN Routing. Also consult your IOS Configuration Guide Book (specific to your version of IOS of course).

Good luck

New Member

Re: dhcp using cat 3550 EMi

1. I have 4 cat 3550, each 3550 for each department.

2. why do I need a router if the cat3550 and cat4507 are capable of routing between vlans ? I am using trunking between 4507 and each 3550.

3. can I create 4 sub-interfaces or vlan interfaces on the 4507, each sub-interface for each department VLAN. and assign ip helper-address to each vlan interface.

can I still assing ip address for different Vlans from one dhcp server ?

The dhcp server is in separate vlan

thank you for your response