Connectivity Guide

DHCP Option Description
● 8 — DHCPINFORM
Parameter
request list
55 — Parameters the server requires for DHCP clients. This is a series of octets where each octet is a
DHCP option code
Renewal time 58 — Amount of time, after the IP address is granted, that the client attempts to renew its lease with the
original server
Rebinding time 59 — Amount of time, after the IP address is granted, that the client attempts to renew its lease with
any server, if the original server does not respond
Vendor class
identifier
60 — User-defined string the Relay Agent uses to forward DHCP client packets to a specific DHCP
server
User port
stacking
230 — Stacking option variable that provides the DHCP server stack-port details when the DHCP offer is
set
End 255 — Signal of the last option in the DHCP packet
DHCP server
The Dynamic Host Configuration Protocol (DHCP) server provides network configuration parameters to DHCP clients on
request. A DHCP server dynamically allocates four required IP parameters to each computer on the virtual local area network
(VLAN) — the IP address, network mask, default gateway, and name server address. DHCP IP address allocation works on a
client/server model where the server assigns the client reusable IP information from an address pool.
DHCP automates network-parameter assignment to network devices. Even in small networks, DHCP makes it easier to add new
devices to the network. The DHCP access service provides a centralized, server-based setup to add clients to the network. This
setup means you do not have to manually create and maintain IP address assignments for clients.
When you use DHCP to manage a pool or IP addresses among hosts, you reduce the number of IP addresses you need. DHCP
manages the IP address pool by leasing an IP address to a host for a limited period, allowing the DHCP server to share a
limited number of IP addresses. DHCP also provides a central database of devices that connects to the network and eliminates
duplicate resource assignments.
Automatic address allocation
Automatic address allocation is an address assignment method that the DHCP server uses to lease an IP address to a client from
a pool of available addresses. You cannot configure an empty DHCP pool, under a DHCP pool configuration. For a successful
commit, you must have either a network statement or host/hardware-address (manual binding) configuration. An IP address
pool is a range of addresses that the DHCP server assigns. The subnet number indexes the address pools.
1. Enable DHCP server-assigned dynamic addresses on an interface in DHCP <POOL> mode.
ip dhcp server
2. Create an IP address pool and provide a name in DHCP mode.
pool name
3. Enter the subnet from which the DHCP server may assign addresses in DHCP <POOL> mode. The network option specifies
the subnet address. The prefix-length option specifies the number of bits used for the network portion of the address
(18 to 31).
network network/prefix-length
4. Enter a range of IP addresses from the subnet specified above, which the DHCP server uses to assign addresses in DHCP
<POOL> mode.
range {ip-address1 [ip-address2]}
NOTE:
Configure at least one interface to match one of the configured network pools. An interface matches a network
pool when its IP address is included in the subnet defined for that network pool. For example, an interface with IP
address 10.1.1.1/24 matches a pool configured with network 10.1.1.0/24.
124 System management