04-24-2019 07:59 AM
I am looking for some clarification on two different setups for multiple DHCP members. From what I can tell I can either add two grid members under the "Member Assignment" for a DHCP Network or I can configure a Failover Association and add that Failover Association to the DHCP network instead of the members.
My question is how does adding two members to the Network work differently than creating a Failover Association and adding the Association to the network? I would be configuring the Failover association as 100% on the primary so it's pretty much a Hot Standby setup and not load balancing.
I searched the documentations but couldn't find a clear explanation.
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04-24-2019 09:03 AM
Those are technically two different settings:
- A DHCP Failover Association is assigned to a DHCP Range, not the network.
- For this to function properly, any Grid member within the same Grid that is assigned to the DHCP Failover Association must be assigned to the network before you assign the DHCP Failover Association to a DHCP Range within that network.
Multiple servers can be assigned to a network. You need to be cautious when doing this because without using DHCP Failover, those servers do not talk and if each server is enabled as an authoritative server, clients can be incorrectly denied a lease and conflicts can occur. When in doubt, use a single DHCP server per network and range, or make use of the DHCP Failover Association feature.
04-29-2019 10:49 AM
Note that if you use DHCP Failover association, the recommended split value is 50/50. Even when set to 100/0 or 0/100, the server with 0% will still have 50% of the remaining IP addresses to serve DHCP clients.
Actually, a potential effect of setting the value to 100% on the primary as it is your plan, is that DHCP peers will be constantly rebalancing the remaining IP addresses 50/50. This will increase the communication traffic between the two peers as one DHCP server will be constanly handing IPs out while the other is not handing any IP at all.