Multiple "ip helper-addresses" on a router interface

[dngembus]

How does multiple ip helper-address statements function on a router interface. If anyone knows, your help would be greatly appreciated. So far I'm leaning toward #2 below.

1. Does the router send a DHCP request to the first ip helper-address and the second request to the next ip helper-address?

2. Does the router send all DHCP request to all ip helper-addresses that are configured?

3. Does the router only send DHCP requests to the first ip helper-address that is configured as long as the first helper address responds?

[prafuljaded]

I think #3 makes more sense.If the first ip-helper doesn't help, the router uses the next one.Usually you use multiple ip-helper commands when you have multiple DHCP servers on different subnets.But if you have multiple DHCP Servers in same subnet, specify their IP addresses explicitly.

Hope that helps.

[sachin]

Router will send request to both DHCP servers and whichever server respond first , that IP will be given to client.

[borek]

Router should use all configured helper addresses ! "ip helper-address" is not only for DHCP, but works for other UDP based protocols. Multiple helper addresses for multiple protocol are used eg. for AutoInstall feature.