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DHCP addresses on all VLANs with ip helper?

pgear
Occasional Visitor

DHCP addresses on all VLANs with ip helper?

Hi folks,

I'm trying to work out whether the configuration i'm looking for is possible with the 2800 series switches i have at my disposal: my plan was to have each switch on my network have multiple VLANs configured, and each VLAN get its IP address from DHCP via a single DHCP server on the default VLAN. Unfortunately, it seems that the switch itself doesn't honour the ip helper-address setting, and thus it requires either a DHCP server on every VLAN, or every VLAN configured on the DHCP server, or static IP addresses on the switches. None of these options thrills me - is there any workaround?

Thanks,
Paul
3 REPLIES
Matt Hobbs
Honored Contributor

Re: DHCP addresses on all VLANs with ip helper?

You only need to add the helper-addresses on your switches which are acting as routers.

For most designs, you'll have the one router which has its VLANs defined with the helper-address set.

Your edge switches will have tagged links back to the router. On these you only need to have really one IP address which you will use for switch management purposes only.
Chris Bullock_1
Frequent Advisor

Re: DHCP addresses on all VLANs with ip helper?

you need to make sure that you define your IP helper address on all VLANS. To do so just using the following commands in the conf t mode:
HP2824-8DP(config)# show ip helper-address vlan 2

IP Helper Addresses

IP Helper Address
-----------------

HP2824-8DP(config)#

This tells you if you have a helper address defined for the specified vlan.
Now we need to define the helper address for the vlan.
HP2824-8DP(config)# vlan 2 ip helper-address 10.10.10.20
HP2824-8DP(config)# show ip helper-address vlan 2

IP Helper Addresses

IP Helper Address
-----------------
10.10.10.20

HP2824-8DP(config)# write memory
HP2824-8DP(config)#

As you see it now has a helper address for the specified vlan.
best of luck
chris
pgear
Occasional Visitor

Re: DHCP addresses on all VLANs with ip helper?

Chris: I have the helper address defined on each VLAN. Without that, i wouldn't have expected it to work at all.

Matt: I'd rather have the helper address defined on each switch so that the broadcast traffic is reduced.

Is it possible to define another ProCurve switch as a DHCP relay and then have that switch relay to a server? That would allow me to use a single address for DHCP on each VLAN, and only that switch would need static IPs and routing enabled.