It seems like the plan is coming together.
O – ODR, P – periodic downloaded static route
Ia – IS-IS inter area, * – candidate default, U – per-user static route I – IS-IS, su – IS-IS summary, L1 – IS-IS level-1, L2 – IS-IS level-2 N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2Į1 – OSPF external type 1, E2 – OSPF external type 2 Let’s verify that the default-router portion of our config generated the information that we expected.Ĭodes: C – connected, S – static, R – RIP, M – mobile, B – BGPĭ – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area Let’s examine some additional output:įastEthernet0/1 is up, line protocol is up At this point, it is the only pool on HQ, so it is not surprising that the IP information was pulled from this pool. Notice that the IP address DID come from the pool that was configured with 202 in the third octet. *Mar 1 00:56:05.123: % DHCP-6-ADDRESS_ASSIGN: Interface FastEthernet0/1 assigned DHCP address 209.165.202.1, mask 255.255.255.224, hostname BRANCH2Īs we desired, interface f0/1 on BRANCH2 has requested and received an IP address that was issued by HQ. Now, all that remains is to go to BRANCH2 and set its interface to use DHCP to get its IP address. Whatever your situation, make sure not to leave out the DNS server from your pool. You may use any other DNS server of your choice, or may even be in an environment where an internal DNS server is provided. I am in the habit of configuring a real DNS server in my pools, so I used the next command, dns-server 4.2.2.2 as noted above. I don’t like to set my lease times too low, because I don’t want this unnecessary traffic soaking up network bandwidth. Recall that halfway through the lease time, the host will begin negotiating with the server to keep the same IP address it already has. Lease 8 just sets the lease time to 8 days. We will verify this once the configuration is complete. This command also causes the generation of a default route on a downstream router, or a 0.0.0.0 path on an IP endpoint. The next command, default-router 209.165.202.2, will be the address that any hosts that acquire addresses from this pool will use as their default gateway. (5 host bits, 2 to the 5 th minus 2 is 30.) With a /27 mask, we know there are 30 possible valid host IP addresses. The second line, network 209.165.202.0 /27, lets the router know how many addresses are in the DHCP pool. So help yourself out by choosing a name that jogs your memory. It is funny how much stuff slips out of our heads merely with the passing of time. The text of the name should be selected so that if you, the network admin, come back three months later and examine the config on this router, it will remind you what you were trying to accomplish when you typed it. The first command, ip dhcp pool BRANCH2, is just creating the pool and giving it a name. Let’s examine these commands one at a time. If we begin with BRANCH2, we note that interface f0/1 should receive 209.165.202.1/27 as its IP address. The IP addressing scheme has already been determined for this small network and is noted in the upper right of the diagram. In an actual scenario, one would normally begin by determining the IP addressing scheme to use so that the address pools will coordinate with the host requirements. What I want to do is to configure one pool on HQ to serve IP addresses to BRANCH2 and one pool to serve IP addresses to BRANCH3. I have built a small networking environment with which to test and troubleshoot the config, so let’s get started.
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This blog will address the configuration of DHCP pools on Cisco routers as well as how to verify that addresses from the correct pools have been distributed.