Microsoft Server 2012 Dhcp Failover Protocol
How does MCLT help ensure that any leases the failed server may have given out while out of contact with it's partner will have expired?For example, if a scope has 1 day lease expiration. Server A give 192.168.2.50 to ClientA and then crashed before being able to sync that info to Server B.If the MCLT is 15 minutes, my understanding is that when ServerB will operate in Partner Down, it will wait the MCLT before taking over the whole scope. So, what will prevent Server B to give 192.168.2.50 once Partner Down + MCLT(15min in thatcase) is reached. It could still give that 192.168.2.50 ip, no?
It's based on the free IP range you've configured.Quoted:'The standby server will take over the free IP address pool of the active server only after it transitions into Partner Down state from Communicated Interrupted state and a time period of MCLT (Maximum Client Lead Time) has expired. This is as per the. To enable the standby server to serve new IP address leases to clients during this interim period - i.e. Till it transitions to Partner Down and takesover the entire free IP address pool of a scope – a percentage of free IP address pool needs to be available to standby server. This can be provided by the configuration parameter – reserve address percentage.'
The above was quoted from the link below, which should further explain it:DHCP Failover Hot-Standby Mode, teamdhcp MSFTAce FekayMVP, MCT, MCITP/EA, MCTS Windows 2008/R2 & Exchange 2007, Exchange 2010 EA, MCSE & MCSA 2003/2000, MCSA Messaging 2003Microsoft Certified TrainerMicrosoft MVP - Directory Services Technical Blogs & Videos:This post is provided AS-IS with no warranties or guarantees and confers no rights. Hi,Thanks for the post.The Maximum Client Lead Time (MCLT) is additional time provided to a DHCP client after expiration of a DHCP lease.
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The MCLT is transmitted from the primary to the secondary server in the CONNECT message, and is the maximum amount of time that one server canextend a lease for a client beyond the time known by the partner server.The 1 minute MCLT value used here is for test lab purposes only, to prompt lease renewal by the client. In a production environment, you should use a longer MCLT, such as 1 hour.Quote fromRegarding the question, in my opinion, there is no need to worry about it. Due to when the partner server is down, the standby server can help to renew IP lease duration for the existing DHCP clients.More information:Hope this helps.Jeremy WuTechNet Community Support. It's based on the free IP range you've configured.Quoted:'The standby server will take over the free IP address pool of the active server only after it transitions into Partner Down state from Communicated Interrupted state and a time period of MCLT (Maximum Client Lead Time) has expired. This is as per the. To enable the standby server to serve new IP address leases to clients during this interim period - i.e. Till it transitions to Partner Down and takesover the entire free IP address pool of a scope – a percentage of free IP address pool needs to be available to standby server.
This can be provided by the configuration parameter – reserve address percentage.' The above was quoted from the link below, which should further explain it:DHCP Failover Hot-Standby Mode, teamdhcp MSFTAce FekayMVP, MCT, MCITP/EA, MCTS Windows 2008/R2 & Exchange 2007, Exchange 2010 EA, MCSE & MCSA 2003/2000, MCSA Messaging 2003Microsoft Certified TrainerMicrosoft MVP - Directory Services Technical Blogs & Videos:This post is provided AS-IS with no warranties or guarantees and confers no rights. Hi,Thanks for the post.The Maximum Client Lead Time (MCLT) is additional time provided to a DHCP client after expiration of a DHCP lease. The MCLT is transmitted from the primary to the secondary server in the CONNECT message, and is the maximum amount of time that one server canextend a lease for a client beyond the time known by the partner server.The 1 minute MCLT value used here is for test lab purposes only, to prompt lease renewal by the client.
How To Configure Dhcp Failover
In a production environment, you should use a longer MCLT, such as 1 hour.Quote fromRegarding the question, in my opinion, there is no need to worry about it. Due to when the partner server is down, the standby server can help to renew IP lease duration for the existing DHCP clients.More information:Hope this helps.Jeremy WuTechNet Community Support.