dhcp relay in rv042?

Discussion in 'Cisco Small Business Routers and VPN Solutions' started by cypher, Mar 2, 2009.

  1. cypher

    cypher Addicted to LI Member


    I'm looking for a way to allow dhcp relay in a rv042. The DHCP server is on another subnet, and I need to be able to use this other DHCP Server, since it is integrated with Active Directory and DNS. I'm not finding what I need to set in the web gui. If it's not in the web gui, does anyone know of a telnet command to specify the DHCP server?

    I'm using the RV042 of a slow IP class C to Class A migration.

    Cisco calls this ip helper command.

    Some may know it as DHCP Forwarding, DHCP Relay, or DHCP Helper.
  2. ifican

    ifican Network Guru Member

    I dont know of any soho devices that do it reliably. Its one of those defining features that you find in more capable devices. Can you be more specific of what you are trying to do? DHCP relay is not going to do you any good if you are still having the rv042 doing the routing for the subnet that is "behind" it.
  3. cypher

    cypher Addicted to LI Member

    Well the subnet behind the router has all of our servers and network infrastructure. Problem is that's on a Class C network 192.yadda yadda yadda.

    Were just about out of IP addresses on that Class C, so were going to migrate to a Class A, but not something that we want to do in one weekend. So with the router and two 48 port switches, we are slowly migrating devices to a Class A network on a group of switches that connect to the rv042, which that routes to the original Class C network.

    Now it's fine the way things are with the static assignments, but we really want to go DHCP. I want to activate DHCP on our Active Directory/DNS server. Like I said before, that server is on the Class C network. So if we create a scope for through, devices on the other side of the router will not be able to get DHCP DISCOVER messages routed across to the Class C network (because that's broadcast). DHCP Offer messages then will never be sent from the server on the Class C network to the Class A network.

    So just say for example, our DHCP server is on, How would be get computers on the other side of the rv042 to get DHCP leases from this server?

    We already enabled telnet and set the proper commands to allow the subnet routing on the rv042. ie) to and that appears to work fine.

    I don't want the rv042 to handle DHCP, because I want our own DHCP server which is integrated with Active Directory to handle it. Besides I don't think the DHCP server in the rv042 can dish out more than 254 host addresses.
  4. cypher

    cypher Addicted to LI Member

    Well what if I multihome the Domain Controller that I want to add the DHCP role to? It has two NICs.

    So I keep one NIC connected to the switches on the old subnet for the migration phase, and make a new connection to the second NIC connected to the switches designated for our Class C to Class A upgrade.

    Would that cause any issues on a Domain Controller/DNS/DHCP server?
  5. DocLarge

    DocLarge Super Moderator Staff Member Member

    Has the possibility of using vlans routed through a Cisco switch been explored, particularly a 3550?
  6. cypher

    cypher Addicted to LI Member

    Yes, we have a quote to overhaul the entire network with Cisco. It's not cheap, so I'm not sure if it will be doable this year. Knowing the dollars we will be able to budget for it next year.
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