DHCP Failover Load Balance Mode

re: DHCP Failover Load Balance Mode

teamdhcp — Mon, 22 Apr 2013 10:14:04 GMT

When a client sends a request for a new lease, it will get lease for MCLT duration. When the client attempts to renew the lease at half the lease period i.e. MCLT/2, it will be given the scope lease duration if DHCP failover is in NORMAL state.

This is as per the DHCP failover protocol. This does increase the traffic from new clients but given the scalability of Windows DHCP server, this should not pose any deployment problem.

re: DHCP Failover Load Balance Mode

Hi, teamdhcp — Mon, 22 Apr 2013 03:28:05 GMT

I got a question here.

If the failover pair stay in Normal status, which lease time will the client obtain? MCLT or the time defined in the Scope configuration.

My test result is MCLT, I think it is unreasonable as it double the request traffic of DHCP.

According most of document of failover, MCLT should and ONLY be actived when failover enter COMMUITCATE-INTERRPUT or PARTER-DOWN status.

I'm confused.

re: DHCP Failover Load Balance Mode

teamdhcp — Tue, 18 Sep 2012 05:11:09 GMT

Joe, yes, client 1 will get the same IP address again. There are two cases possible -

1. DHCP 1 synced the IP address 10.2.3.4 to DHCP2 before it went down.

In this case, the client will given the full lease duration which has been configured for the scope.

2. DHCP 1 went down before syncing the IP address 10.2.3.4 to DHCP2

In this case also, the client will be able to renew but the lease duration will be shorter - same as the value configured for MCLT.

There is another client behavior to be aware of here - at half the lease period, the client will attempt to renew the lease. This is just normal DHCP client behavior as per the DHCP protocol. The renew message is unicast. So in the scenario above, it will be directed to DHCP 1 which is down and so there will be no response. At 7/8th of the lease period, the client will broadcast the renew request message. This message will be seen by DHCP2 which will respond to the renew request.

re: DHCP Failover Load Balance Mode

Joe — Mon, 17 Sep 2012 16:12:02 GMT

Question:

If client1 gets an IP address of 10.2.3.4 from DHCP1 and then DHCP1 goes down but is in a load balance failover pair with DHCP2 and client1 does a renew - will client1 get the same IP address again?

In other words - Does DHCP2 have IP to MAC address mapping for both pairs in the load balance?

re: DHCP Failover Load Balance Mode

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