Now let's go ahead and look at scopes and superscopes. Scopes are IP address ranges assigned in a DHCP server. Different groups of computers are assigned different scopes inside the DHCP server and other DHCP servers on the network. Most scopes are going to cover a traditional IP address range. However, upon occasion you may need to configure a DHCP server that uses a non-traditional IP range.
One type of non-traditional IP range is the superscope. A superscope is actually designed to collect multiple scopes together into one superscope. This is very useful when you have more clients connected to a segment of your network than your DHCP server can actually handle in the scope that it was assigned. Let's look at a scenario that illustrates this point. Let's say we have a DHCP server and it was assigned the 184.108.40.206/24 range.
Let's further assume that we've taken the first 20 IPs in this range and we preserved them for static IP usage for things like servers and that sort of thing. As a result, we have a maximum of 234 IP addresses that we can assign using DHCP in this range. What happens as the clients approach 234 systems trying to access DHCP and get assigned IP addresses, the DHCP begins to fail.
What that means is some assignments aren't made, some requests are missed, things like that. And as we get closer and closer to the limit, we finally get to the point where the DHCP server is unable to assign any additional IP addresses. The result is that any computers on that segment beyond these first 234 or so computers will not be able to get IP addresses and, therefore, will not be able to get on the network. To fix this, we need to have more IP addresses for this particular segment.
The way we do that is creating a superscope. The superscope is what provides a solution for this. Basically, in this scenario, what we would do is create a second scope of four additional IP addresses. In our case, let's say we create a second scope that is 220.127.116.11/24. As you remember, the previous range that we had was .2.0/24 and so now we have added .2.0/24.
The result is that we've basically doubled the number of IPs that this server can assign to this segment. Now why is the scope necessary, it's necessary because a DHCP is only able to provide IPs to the segment to which the NIC inside the DHCP server is connected to. In traditional scopes, the DHCP server only uses IP addresses or IP address ranges that correspond to the DHCP server that's being used the primary address of that DHCP server.
As a result, what this means is I can only assign IPs by DHCP that are in a range that DHCP server resides on itself. With the superscope, I can actually take multiple traditional scopes and unify them into one superscope. When this happens, I can then set up my DHCP server to provide leases for all the IP addresses in the superscope rather than just the limited number of IPs in the scope that the DHCP server would traditionally have to use.
Now, in our example so far we used contiguous or ranges that are one right after the other. We went from a .1.0/24 to a .2.0/24. Well what happens if we don't have a .2.0 range that matches the one that we just used. In that case, we can use a noncontiguous range. A noncontiguous range is when the two ranges being used are not one after the other or next to each other in the ranges.
In this scenario, if the .2.0 range wasn't available then we'd have to use a different range. So, let's say that we don't have the .2.0 range but we do have the .11.0 range. And so what we'll do is create a scope with the 18.104.22.168/24 range and then we can add it to the 22.214.171.124/24 range and create a superscope out of these two noncontiguous ranges.
Now like everything else, there are limitations to the superscopes. One of the things about superscope, is every time you add a scope to a DHCP server that becomes a logically a new segment in the network. The scopes cannot talk to each other except through a router when we do this. What that means is that the second scope will need its own default gateway. In other words, I can't use the same default gateway for both of my scopes. Also, this means that I have to use a second NIC to enable the routing between the two segments.
In other words, I set the second NIC and I allow to the two NICs to talk to each other. In this way, I can now provide IPs on both the ranges because the two ranges are now able to talk to each other via the second NIC. Now, one thing we can do if we don't have a second NIC is certain types of routers will actually allow you to assign two different addresses to the same NIC. In other words, we have one NIC but that port on the NIC gets two different addresses and, therefore, can address two different ranges.
The Microsoft Routing and Remote Access service actually allows us to do this. That is the routing service that's built into the Microsoft server environment. We'll actually talk about the Routing and Remote Access service later in this course.
This Windows training course helps you study for the exams while learning advanced server administration techniques. Professor Timothy Pintello covers all of the core exam topics, including DHCPv6, primary and secondary DNS zone configuration, working with different DNS resource record types, VPN routing, certificates for direct access, IPAM admin delegation, and more.
- Implementing advanced DHCP solutions
- Configuring DNS zones
- Configuring DNS records
- Implementing advanced DNS solutions
- Configuring VPN and routing
- Configuring direct access
- Deploying and managing IPAM