How to configure a switch to support PXE esp. when switch is providing DHCP service and L3 routing for multiple VLANs

[Sunil Gajjar]

I am looking to configure a switch to support PXE, it works straight by adding ip-helper statements in normal scenario when DHCP service is running on box other than the switch having SVIs configured. However in a special case, I am trying to configure a switch which has multiple SVIs for respective VLANs and it is also hosting DHCP service so I believe ip-helper statement is ignored as it has a DHCP scope that is valid to service the request.

It is a critical office with hundreds of users and moving DHCP is not a preffered option so it would be a great help if someone can guide with required configuration on the switch to support PXE in this case.

Thanks already!

[Richard Burts]

I do not have a lot of experience with PXE, but I will offer these suggestions and hope that they help.

- having DHCP configured on the switch does not mean that the ip helper-address is ignored. The helper address will still forward the broadcast request as a unicast to the configured helper address. So the PXE server should still get a copy of the request.

- I believe that the PXE request is a slightly modified DHCP request. So it is possible that the switch DHCP will not respond to the request. And the worst case scenario is that the PXE client receives two responses, one from the switch and the other from the PXE server. So the client would need to choose the correct offer.

HTH

Rick