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Beginner

1 VLAN, 2 IP Address, 2 Helper / DHCP Servers

Hello,

I'm currently looking at this issue where I want to maintain my vlan but change IP Addresses (gradually).  My vlan looks as follows and all works well, however I want to add a secondary IP Address for my new range with ip helper-address for that new network.  Does anyone know how I can have hosts on the 10.217.4.1 subnet go to the 10.217.1.10 dhcp server and not the one of the primary address (10.218.1.10)?

interface Vlan10
ip address 10.218.4.1 255.255.254.0
ip helper-address 10.218.1.10
##ip address 10.217.4.1 255.255.254.0 secondary
##ip helper-address 10.217.1.10

Thanks,

Peter

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1 ACCEPTED SOLUTION

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Beginner

Hi,

Hi,

if you just deploy both helper-addresses, the router will forward the DHCP requests to both servers. I don't think there is a way to control that from the router. Your best option is to control it from the DHCP servers by filtering MAC addresses so you can select which server is going to assign the IP address to each host in your network.

Regards,

Julio

3 REPLIES 3
Beginner

Hi,

Hi,

if you just deploy both helper-addresses, the router will forward the DHCP requests to both servers. I don't think there is a way to control that from the router. Your best option is to control it from the DHCP servers by filtering MAC addresses so you can select which server is going to assign the IP address to each host in your network.

Regards,

Julio

Beginner

Ah ok, I'd hoped there would

Ah ok, I'd hoped there would be a way to do it at the router, different VLAN it is!

Enthusiast

You could just enable

You could just enable forwarding to the new DHCP server.  Remember that the older leases will still function, and will be able to RENEW existing leases, as they send the request directly to the DHCP server "they know about" as that's part of the lease information.

As they disconnect and reconnect, the old DHCP and address range will all expire, except for clients that never power down.

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