DHCP ON Cisco Routers

DHCP ON CISCO Router-  Dynamic Host Configuration Protocol (DHCP), is used to automatically assign network parameters like IP address, mask, gateway, and DNS information to network clients. While DHCP server services are traditionally deployed on network servers, it isn’t uncommon to see a DHCP server role configured on a router or switch in smaller environments. Enable The DHCP Server Service The first step is to enable the DHCP server service on the router. BranchRouter# configure terminal BranchRouter(config)# service dhcp Define The DHCP Pool Now we define the range of addresses the router should assign to client requests. The range is referred to as a pool. BranchRouter(config)# ip dhcp pool MARKETING BranchRouter(dhcp-config)# network 172.16.1.0 255.255.255.0 In this example, the statement network 172.16.1.0 255.255.255.0 directs the router to issue IP addresses to clients using range 172.16.1.1-172.16.1.254. This defines the whole subnet for the client scope. That’s not a good practice since we need other devices on the segment (like the router’s gateway IP address). We’ll add a list of addresses to exclude in just a minute. Before we do that we need define additional DHCP parameters we want to define for the DHCP leases. ​DHCP Parameters Clients need information like a gateway address, primary and secondary DNS servers, domain name to use, and DHCP lease period. BranchRouter(dhcp-config)# default-router 172.16.1.1 BranchRouter(dhcp-config)# dns-server 172.16.100.54 172.16.100.55 BranchRouter(dhcp-config)# domain-name Abhishek.com BranchRouter(dhcp-config)# exit There are numerous DHCP options you can assign, but here are a few of the more common: domain-name – Defines the domain name the client should use dns-server address [address2] – Lists the DNS servers (in order of preference) the client should use default-router – Defines the client’s gateway lease {days [hours [minutes]] | infinite} – Defines the lease duration (default is 24 hours) Define The Exclude List The last step is to define the client exclude list to the DHCP scope. In this case we exclude the first 99 IP addresses for use by the local router interface and other statically-assigned devices like servers. This effectively makes the client range 172.16.1.100-172.16.1.254. BranchRouter(config)# ip dhcp excluded-address 172.16.1.1 172.16.1.99    After you have enabled the DHCP service, defined the DHCP lease pool, DHCP parameters, and a DHCP exclude list, the DHCP service will be active and responding to client requests. Pretty simple. Viewing Client Leases After the DHCP server configuration is in place on the local router or layer 3 switch, you can use the show ip dhcp binding command to view the active DHCP client leases issued. Router#show ip dhcp binding Bindings from all pools not associated with VRF: IP address        Client-ID/              Lease expiration        Type Hardware address/ User name 172.16.1.100        24d9.1c2b.7aa2          June 15 2016 11:39 AM    Automatic 172.16.1.101        24d9.1c2b.5c74          June 15 2016 11:42 AM    Automatic 172.16.1.102        24d9.1c2b.ac21          june 15 2016 11:47 AM    Automatic 172.16.1.103        24d9.1c2b.5dd6          june 15 2016 11:53 AM    Automatic