Server 2012 DHCP Part 1

DHCP.. yes it is . Most administrators love this as its help them to be safe in there client network areas with the IP address assigning tasks. According to (IETF) this is a standard. This has come with many windows server releases. Windows server 2008 didn’t make a huge change to the DHCP server service on server manager. To reduce the complexity of host IP addresses in a TCP/IP network DHCP is the champ of the battle. When Microsoft release Windows server 2012, DHCP armed with new features. Basically we can see three major improvements

• DHCP Failover
• Policy Based Assignment
• PowerShell for DHCP server management

In real world examples we have different kind of DHCP issues if it is not configured properly. If we talk about above mentioned features the first feature is the best in my environment. To provide DHCP server service continuously to the subnet is a real help to get rid of  some server failing errors.

The basic concept of DHCP failover is its making happen to replicate lease information between two DHCP servers in your network (Subnet). If one server gone down the other DHCP server can take the responsibility to serve to clients of the subnet without making any delay errors.

Microsoft has given another option for this failover system. You can configure both DHCP servers with Load Balancing configurations. This will allow sending all client requests in a distributed manner for both servers. If the client requests are huge you can use this method successfully in your network to balance the request and service load.

When configuring failover settings in DHCP servers. You should keep following things in your mind

DHCP failover feature is supporting only for two servers that is serving for once subnet or scope also it will support its relationship only for IPv 4 scopes and subnets.

Above details are very important to keep in your mind when thinking about DHCP failover configurations in the network. These configurations are going under two modes. First one is Hot Standby Mode and the other one is Load Sharing Mode. From the words you can imagine the process which are expressing. I think its better to discuss both modes separately.

Hot Standby Mode

This mode is very simple to understand as it is like a one vehicle with two drivers. If one driver went down or unreachable, the other one will take the responsibility of driving the vehicle. Technically we explain it as below.

You have two servers configured as DHCP servers with Hot Standby Mode. Primary DHCP server has the responsibility to leasing IP address and configuration information to the subnet or scope. If the primary DHCP server went down the secondary DHCP server is taking all the responsibilities which had with primary DHCP server and it is starting to server the subnet or to the scope.

The best thing is that your secondary DHCP server could be a secondary server for another subnet if you configured it to serve those subnets too.

See the figure given below to clearly understand the meaning of above sentence.

 Microsoft suggest to use this Mode for an central location which the servers are serving as backup servers and standby severs which are serving for servers and clients in remote locations. In above figure you can see that the central locations DHCP secondary server is configured to serve to all other three primary DHCP server sites.

I will discus about the other mode of DHCP failover configurations in my next post. :)