Switches, Hubs, and Modems
cancel
Showing results for 
Search instead for 
Did you mean: 

ip helper best practices

RobB_8
Advisor

ip helper best practices

I have a question about using ip helper. If I have a class C subnet with a server inside the subnet which does DHCP, and I have a 2nd failover DHCP pool offsite at another class C subnet do I need an ip helper statement for both the local and the other one across the wan...
It seems that if I only have the ip helper for the off site DHCP and not the local one, the broadcasts do go out to get an IP locally and in most cases the local one is found, but I do see leases in the redundant pool from time to time when I know there are no server outages onsite.
thoughts?
2 REPLIES
Mohieddin Kharnoub
Honored Contributor

Re: ip helper best practices

Hi

Broadcasts never cross wan, its terminated by the routers.
For you scenario, you better have a look at this:
http://www.hp.com/rnd/support/config_examples/5300xl_dhcp_relay.pdf

Good Luck !!!
Science for Everyone
Carsten Reinhard
Frequent Advisor

Re: ip helper best practices

Hi RobB,

there are some Microsoft Best practices which say, that you have to set up an delay on the secondary DHCP Server (as I remember about 4 seconds, but it may vary). Otherwise both DHCP-Server will answer the DHCP-Request from the client at nearly the same time.

Greetings Carsten.