Configure DHCP in router cisco

Configure DHCP in router cisco

- in Enterprise Infrastructure

DHCP (Dynamic Host Configuration Protocol) 

The DHCP protocol allows clients to dynamically configure network parameters without the need for a manual configuration process.  Dynamically assigns an IP address to the client, subnet mask, default gateway, DNS server, lease time, etc.

The four basic DHCP phases:

  • Step 1.- DHCP Discover.- Broadcast message from a client to find a dhcp server
  • Step 2.- DHCP Offer.- DHCP server response from the client’s DISCOVER message. This message contains the network information provided by the dhcp server, such as client ip, subnet mask, gateway, dns server, etc. 
  • Step 3.- DHCP Request. The client’s message is used to respond to the DHCP server and accept the information provided in step 3.
  • Step 4.- DHCP Ack.- The DHCP server sends you acknowledgment to confirm the lease.

DHCP server configuration in router:

Switch(config)# ip dhcp excluded-address ////Exclude a range of IP addresses from being delivered automatically.

Switch(config)# ip dhcp pool Users //Assign a name to the address pool

Switch(dhcp-config)# network
Switch(dhcp-config)# default-router
Switch(dhcp-config)# dns-server

Switch(dhcp-config)# lease infinite //Lease time for the client, can be configures by day, hour and minutes


Switch# show ip dhcp binding //Show all IPs assigned by the server

Switch# clear ip dhcp binding * //Delete all DHCP leases

Switch# debug ip dhcp server packet|events //View real-time dhcp discover, offer, request and ack.

DHCP Relay – Relay Agent

It used to forward DHCP messages to DHCP servers on remote networks. It converts the packets to unicast and delivers them to the IP configured as a DHCP server.

It is applied on the physical interface or SVI, so no DHCP pools are created.


Switch(config)# interface vlan 1
Switch(config-if)# ip helper-address

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