In this article, we will cover more advanced DHCP features and topics such as server options, superscopes, multicast scopes, dynamic DNS, DHCP database backup and restoration, DHCP migration, and DHCP troubleshooting. We will cover these topics in two ways: by building out from our earlier implementation and by using our imagination!
Ok, using our imagination for this purpose may seem silly but doing so will give us the opportunity to indirectly learn how, why, and where these advanced DHCP features and topics come into play in a real-world network and how other networking technologies are involved in a DHCP implementation.
We will imagine that we are building our DHCP server for a company that has two buildings, Building A and Building B, each with a single floor (for now). Building A is on a 192.168.0.0/24 network and Building B is on a 192.168.1.0/24 network.
Although each building has its own DNS server (192.168.0.252 and 192.168.1.252), WINS server (192.168.0.251 and 192.168.1.251) and Cisco Catalyst 4507R-E switch (192.168.0.254 and 192.168.1.254), only a single DHCP server exists – it is the one that we have been building and it resides in Building A.
The clients and servers in each building connect to their respective Cisco Catalyst switches and the switches are uplinked to a Cisco router for Internet connectivity. The only notable configuration is with the Building B switch: It is configured with the ip helper-address 192.168.0.253 command.
The ip helper-address command tells the switch to forward DHCP requests in the local subnet to the DHCP server, since the clients in Building B cannot initially communicate with the DHCP server directly. We are not concerned with any other configuration or networking technologies for now.
The specifications of our imaginary company state that the company has two buildings – Building A and Building B. In our first article, we created a scope called “Building A, Floor 1” so a scope for our first building is already made. In this article, we will create a scope for Building B, Floor 1, using the instructions from our Basic DHCP Configuration article and the following specifications for the scope:
After creating the scope, we want to activate it as well.
Notice that, in creating this scope, we had to input a lot of the same information from our “Building A, Floor 1” scope. In the event that we had several other scopes to create, we would surely not want to be inputting the same information each time for each scope.
That is where server options are useful. Server options allow you to specify options that all the scopes have in common. In creating two scopes, we noticed that our scopes had the following in common:
- DNS servers
- WINS servers
- Domain name
To avoid having to enter this information again, we will create these options as server options. To do this:
1. On the DHCP MMC, right-click Server Options and choose Configure Options