Change DHCP network for end users

[Mitchell Theriot]

What is the best way to change vlans so that clients pull dhcp from another scope with the least amount of network disruption?  For example lets say i have vlan 5 that is 172.16.5.x and vlan 10 that is 172.16.10.x configured on a switch.  The access ports are currently configured for vlan 5 so my clients pull a dhcp ip from that network.  We no longer want to use dhcp on the 172.16.5.x network so I want to change my dhcp clients to pull from the 172.16.10.x.  What is the best way to do that?  I know I can simply change the vlan assigment on the ports but that would immediately break their connections.  is their a way that is less disruptive so that say when their dhcp lease in 172.16.5.x expires they pull a new address from the 172.16.10.x?                

[Richard Burts]

I would think that you could achieve this by using a secondary address. As long as you are content to let the layer 2 vlan connection remain in VLAN 5 and change the IP subnet and its addressing. Configure the interface vlan 5 to make the primary address 172.16.10. x and to make 172.16.5.x secondary. This will allow all the devices with current leases to continue to operate and to access their configured gateway. As leases expire the client will obtain its new address from the scope for 172.16.10.0.

If you really want to move them from layer 2 vlan 5 to layer 2 vlan 10 then I can not think of how to do that without disruption.

HTH

Rick

[Mitchell Theriot]

What would happen if I trunked the ports the clients are using allowing both vlans and then disable the dhcp scope for vlan 5?  When the clients request a renewal the vlan 5 scope would no longer respond.  Would they then send out a dhcp broadcast request that would also go out vlan 10 and discover the new scope which we would have setup?  Once all clients are moved over I could return the ports to access mode on vlan 10.

[pille1234]

Mitchell Theriot schrieb:
 What would happen if I trunked the ports the clients are using allowing both vlans and then disable the dhcp scope for vlan 5?  When the clients request a renewal the vlan 5 scope would no longer respond.  Would they then send out a dhcp broadcast request that would also go out vlan 10 and discover the new scope which we would have setup?  Once all clients are moved over I could return the ports to access mode on vlan 10.

That would certainly  not work and would cause a disruption, as the clients do not know how to handle vlan tagged frames.

[pille1234 · Accepted solution]

Why not wait till end of office hours, change vlan assignments and shut/no shut the ports, takes less than  30 seconds when using range commands. This way all PCs still running will get a new IP address immediately. People don't work 24/7 at your site, do they?

Regards Pille

[Mitchell Theriot]

Pille, no they do not work 24/7 so that may work.  Thanks.