DHCP + HSRP best practice

[tomstephens89]

Installing a pair of Nexus 3064's to replace a stack of Catalyst 3750's . I will be using VPC and HSRP since I can no longer stack.

I know how to create DHCP pools on a single Cisco switch and tie that to an SVI however i'll be running HSRP and want to provide DHCP in a redunant configuration. If I only have the pools on the active hsrp switch, should that fail, I have no DHCP.

If I duplicate the pools on the standby, yes I will have DHCP function should the primary fail, however this is likeley going to end up with duplicated IP's being issued where they are already in use by client due to the fact that the switches do not syncronise their binding table.

Is the best solution to use a third party DHCP server such as with a Linux/Windows server which I can simply multihome into the two switches with an LACP Trunk carrying all VLAN's? Or just set the DHCP helper address on the SVI's on both switches pointing to my DHCP server in its assocated VLAN?

Help appreciated.

[ADP_89 · Accepted solution]

Hello Tom,

Your statements are all correct. The 2 hypothesis you made could be both valid but the best one actually depends on your environment. If you have a single VLAN I would suggest you to dual home a server with DHCP server software to both Nexus(or connect it to a multihomed child switch) and let it manage all the DHCP functions. Instead if you have multiple vlans, or if you plan to add new vlans, the best solution would be to have the ip helper function enabled on the SVIs so all the DHCP requests will be passed to a proper server.

HTH,

ADP

[tomstephens89]

Thanks, that confirms my thoughts about having to use a third party DHCP server.