IP Routing for DHCP Relay

[Mokhalil82]

Hi

We have 2960x switches at many sites as in the attached topology. SW1 has ip routing enabled and has the ip helpers, but the ISP router is the gateway for the networks. The reason would be that if we ever change the DHCP server IPs we do not have to go via the ISP. SW2 and SW3 have ip routing disabled.

My question is can SW1 still act as a DHCP relay, if the following commands are applied?

no ip routing

no ip redirects

no ip proxy-arp

no ip unreachables

ip dhcp bootp ignore

All the commands are already applied to Switches 2 & 3. 

[paul driver]

Hello

If that switch isnt perfroming any routing functions , then yes disable ip routing,.

FYI - you only need a dhcp helper if the dhcp server resides off you network, As the router is perfroming the routing which includes I am assuming the MGT addressing of the switch(s) then it should be fine.

However before you disable ip routing, apply a default-gateway to the switch,it will only be valid away once routing is disabled.

res

Paul

[Mokhalil82]

The DHCP does reside on a different network hence the ip helpers on the switch. The question is though, is ip routing required on that switch for it to act as a dhcp relay.

The router is manhed by the isp and is the gateway for all the networks using sub interfaces i presume. So the only reason to have the ip hepers on the switch os so we dont have to go via the isp if we change our dhcp servers.

[paul driver · Accepted solution]

Hello

Assuming that switch has the only one SVI active and that's the MGT address, the switch should be able to relay dhcp requests

Make sure it has a default-gateway

res

Paul