DHCP Server Commands

This section describes the commands you to configure the DHCP server settings for the switch. DHCP uses UDP as its transport protocol and supports a number of features that facilitate in administration address allocations.

ip dhcp pool

This command configures a DHCP address pool name on a DHCP server and enters DHCP pool configuration mode.

• Default: none
• Format: ip dhcp pool <name>
• Mode: Global Config

no ip dhcp pool

This command removes the DHCP address pool. The name should be previously configured pool name.

• Format: no ip dhcp pool <name>
• Mode: Global Config

client-identifier

This command specifies the unique identifier for a DHCP client. Unique-identifier is a valid notation in hexadecimal format. In some systems, such as Microsoft DHCP clients, the client identifier is required instead of hardware addresses. The unique-identifier is a concatenation of the media type and the MAC address. For example, the Microsoft client identifier for Ethernet address c8:19:24:88:f1:77 is 01:c8:19:24:88:f1:77 where 01 represents the Ethernet media type.

• Default: none
• Format: client-identifier <uniqueidentifier>
• Mode: DHCP Pool Config

no client-identifier

This command deletes the client identifier.

• Format: no client-identifier
• Mode: DHCP Pool Config

client-name

This command specifies the name for a DHCP client. Name is a string consisting of standard ASCII characters.

• Default: none
• Format: client-name <name>
• Mode: DHCP Pool Config

no client-name

This command removes the client name.

• Format: no client-name
• Mode: DHCP Pool Config

default-router

This command specifies the default router list for a DHCP client. {address1, address2…address8} are valid IP addresses, each made up of four decimal bytes ranging from 0 to 255. IP address 0.0.0.0 is invalid.

• Default: none
• Format: default-router <address1> [<address2>....<address8>]
• Mode: DHCP Pool Config

no default-router

This command removes the default router list.

• Format: no default-router
• Mode: DHCP Pool Config

dns-server

This command specifies the IP servers available to a DHCP client. Address parameters are valid IP addresses; each made up of four decimal bytes ranging from 0 to 255. IP address 0.0.0.0 is invalid.

• Default: none
• Format: dns-server <address1> [<address2>....<address8>]
• Mode: DHCP Pool Config

no dns-server

This command removes the DNS Server list.

• Format: no dns-server
• Mode: DHCP Pool Config

hardware-address

This command specifies the hardware address of a DHCP client. Hardware-address is the MAC address of the hardware platform of the client consisting of 6 bytes in dotted hexadecimal format. Type indicates the protocol of the hardware platform. It is 1 for 10 MB Ethernet and 6 for IEEE 802.

• Default: ethernet
• Format: hardware-address <hardwareaddress> <type>
• Mode: DHCP Pool Config

no hardware-address

This command removes the hardware address of the DHCP client.

• Format: no hardware-address
• Mode: DHCP Pool Config

host

This command specifies the IP address and network mask for a manual binding to a DHCP client. Address and Mask are valid IP addresses; each made up of four decimal bytes ranging from 0 to 255. IP address 0.0.0.0 is invalid. The prefix-length is an integer from 0 to 32

• Default: none
• Format: host <address> [{<mask> | <prefix-length>}]
• Mode: DHCP Pool Config

no host

This command removes the IP address of the DHCP client.

• Format: no host
• Mode: DHCP Pool Config

lease

This command configures the duration of the lease for an IP address that is assigned from a DHCP server to a DHCP client. The overall lease time should be between 1-86400 minutes. If you specify infinite, the lease is set for 60 days. You can also specify a lease duration. Days is an integer from 0 to 59. Hours is an integer from 0 to 1439. Minutes is an integer from 0 to 86399.

• Default: 1 (day)
• Format: lease [{<days> [<hours>] [<minutes>] | infinite}]
• Mode: DHCP Pool Config

no lease

This command restores the default value of the lease time for DHCP Server.

• Format: no lease
• Mode: DHCP Pool Config

network

Use this command to configure the subnet number and mask for a DHCP address pool on the server. Network-number is a valid IP address, made up of four decimal bytes ranging from 0 to 255. IP address 0.0.0.0 is invalid. Mask is the IP subnet mask for the specified address pool. The prefix-length is an integer from 0 to 32.

• Default: none
• Format: network <networknumber> [{<mask> | <prefixlength>}]
• Mode: DHCP Pool Config

no network

This command removes the subnet number and mask.

• Format: no network
• Mode: DHCP Pool Config

bootfile

The command specifies the name of the default boot image for a DHCP client. The <filename> specifies the boot image file.

• Format: bootfile <filename>
• Mode: DHCP Pool Config

no bootfile

This command deletes the boot image name.

• Format: no bootfile
• Mode: DHCP Pool Config

domain-name

This command specifies the domain name for a DHCP client. The <domain> specifies the domain name string of the client.

• Default: none
• Format: domain-name <domain>
• Mode: DHCP Pool Config

no domain-name

This command removes the domain name.

• Format: no domain-name
• Mode: DHCP Pool Config

netbios-name-server

This command configures NetBIOS Windows Internet Naming Service (WINS) name servers that are available to DHCP clients. One IP address is required, although one can specify up to eight addresses in one command line. Servers are listed in order of preference (address1 is the most preferred server, address2 is the next most preferred server, and so on).

• Default: none
• Format: netbios-name-server <address> [<address2>...<address8>]
• Mode: DHCP Pool Config

no netbios-name-server

This command removes the NetBIOS name server list.

• Format: no netbios-name-server
• Mode: DHCP Pool Config

netbios-node-type

The command configures the NetBIOS node type for Microsoft Dynamic Host Configuration Protocol (DHCP) clients.

• Default: none
• Format: netbios-node-type <type>
• Mode: DHCP Pool Config

Type Specifies the NetBIOS node type. Valid types are:

• b-node: Broadcast
• p-node: Peer-to-peer
• m-node: Mixed
• h-node: Hybrid (recommended)

no netbios-node-type

This command removes the NetBIOS node Type.

• Format: no netbios-node-type
• Mode: DP PHCool Config

next-server

This command configures the next server in the boot process of a DHCP client.The <address> parameter is the IP address of the next server in the boot process, which is typically a TFTP server.

• Default: inbound interface helper addresses
• Format: next-server <address>
• Mode: DHCP Pool Config

no next-server

This command removes the boot server list.

• Format: no next-server
• Mode: DHCP Pool Config

option

The option command configures DHCP Server options. The <code> parameter specifies the DHCP option code and ranges from 1-254. The <ascii string> parameter specifies an NVT ASCII character string. ASCII character strings that contain white space must be delimited by quotation marks. The hex <string> parameter specifies hexadecimal data. In hexadecimal, character strings are two hexadecimal digits. You can separate each byte by a period (for example, a3.4f.22.0c), colon (for example, a3:4f:22:0c), or white space (for example, a3 4f 22 0c).

• Default: none
• Format: option <code> {ascii string | hex <string1> [<string2>...<string8>] | ip <address1> [<address2>...<address8>]}
• Mode: DHCP Pool Config

no option

This command removes the DHCP Server options. The <code> parameter specifies the DHCP option code.

• Format: no option <code>
• Mode: DHCP Pool Config

ip dhcp excluded-address

This command specifies the IP addresses that a DHCP server should not assign to DHCP clients. Low-address and high-address are valid IP addresses; each made up of four decimal bytes ranging from 0 to 255. IP address 0.0.0.0 is invalid.

• Default: none
• Format: ip dhcp excluded-address <lowaddress> [highaddress]
• Mode: Global Config

no ip dhcp excluded-address

This command removes the excluded IP addresses for a DHCP client. Low-address and highaddress are valid IP addresses; each made up of four decimal bytes ranging from 0 to 255. IP address 0.0.0.0 is invalid.

• Format: no ip dhcp excluded-address <lowaddress> [highaddress]
• Mode: Global Config

ip dhcp ping packets

Use this command to specify the number, in a range from 2-10, of packets a DHCP server sends to a pool address as part of a ping operation. By default the number of packets sent to a pool address is 2, which is the smallest allowed number when sending packets. Setting the number of packets to 0 disables this command.

• Default: 2
• Format: ip dhcp ping packets <0,2-10>
• Mode: Global Config

no ip dhcp ping packets

This command prevents the server from pinging pool addresses and sets the number of packets to 0.

• Default: 0
• Format: no ip dhcp ping packets
• Mode: Global Config

service dhcp

This command enables the DHCP server.

• Default: disabled
• Format: service dhcp
• Mode: Global Config

no service dhcp

This command disables the DHCP server.

• Format: no service dhcp
• Mode: Global Config

ip dhcp bootp automatic

This command enables the allocation of the addresses to the bootp client. The addresses are from the automatic address pool.

• Default: disabled
• Format: ip dhcp bootp automatic
• Mode: Global Config

no ip dhcp bootp automatic

This command disables the allocation of the addresses to the bootp client. The address are from the automatic address pool.

• Format: no ip dhcp bootp automatic
• Mode: Global Config

ip dhcp conflict logging

This command enables conflict logging on DHCP server.

• Default: enabled
• Format: ip dhcp conflict logging
• Mode: Global Config

no ip dhcp conflict logging

This command disables conflict logging on DHCP server.

• Format: no ip dhcp conflict logging
• Mode: Global Config

clear ip dhcp binding

This command deletes an automatic address binding from the DHCP server database. If “*” is specified, the bindings corresponding to all the addresses are deleted. <address> is a valid IP address made up of four decimal bytes ranging from 0 to 255. IP address 0.0.0.0 is invalid.

• Format: clear ip dhcp binding {<address> | *}
• Mode: Privileged EXEC

clear ip dhcp server statistics

This command clears DHCP server statistics counters.

• Format: clear ip dhcp server statistics
• Mode: Privileged EXEC

clear ip dhcp conflict

The command is used to clear an address conflict from the DHCP Server database. The server detects conflicts using a ping. DHCP server clears all conflicts If the asterisk (*) character is used as the address parameter.

• Default: none
• Format: clear ip dhcp conflict {<address> | *}
• Mode: Privileged EXEC

show ip dhcp binding

This command displays address bindings for the specific IP address on the DHCP server. If no IP address is specified, the bindings corresponding to all the addresses are displayed.

• Format: show ip dhcp binding [<address>]
• Modes: Privileged EXEC User EXEC

The display parameters for above command are:

• IP address: The IP address of the client.
• Hardware Address: The MAC Address or the client identifier.
• Lease expiration: The lease expiration time of the IP address assigned to the client.
• Type: The manner in which IP address was assigned to the client.

show ip dhcp global configuration

This command displays global configuration on the DHCP server. If no IP address is specified, the bindings corresponding to all the addresses are displayed.

• Format: show ip dhcp global configuration
• Modes: Privileged EXEC User EXEC

The display parameters for above command are:

• Service DHCP: The field to display the status of dhcp protocol.
• Number of Ping Packets: The maximum number of Ping Packets that will be sent to verify that an ip address id not already assigned.
• Conflict Logging: Shows whether conflict logging is enabled or disabled.
• BootP Automatic: Shows whether BootP for dynamic pools is enabled or disabled.

show ip dhcp pool configuration

This command displays pool configuration. If all is specified, configuration for all the pools is displayed.

• Format: show ip dhcp pool configuration {<name> | all}
• Modes: Privileged EXEC/ User EXEC

The display parameters for above command are:

• Pool Name: The name of the configured pool.
• Pool Type: The pool type.
• Lease Time: The lease expiration time of the IP address assigned to the client.
• DNS Servers: The list of DNS servers available to the DHCP client
• Default Routers: The list of the default routers available to the DHCP client

The following additional field is displayed for Dynamic pool type:

• Network: The network number and the mask for the DHCP address pool.

The following additional fields are displayed for Manual pool type:

• Client Name: The name of a DHCP client.
• Client Identifier: The unique identifier of a DHCP client.
• Hardware Address: The hardware address of a DHCP client.
• Hardware Address Type: The protocol of the hardware platform.
• Host: The IP address and the mask for a manual binding to a DHCP client.

show ip dhcp server statistics

This command displays DHCP server statistics.

• Format: show ip dhcp server statistics
• Modes: Privileged EXEC/ User EXEC

The display parameters for above command are:

• Automatic Bindings: The number of IP addresses that have been automatically mapped to the MAC addresses of hosts that are found in the DHCP database.
• Expired Bindings: The number of expired leases.
• Malformed Bindings: The number of truncated or corrupted messages that were received by the DHCP server.

Message Received:

• DHCP DISCOVER: The number of DHCPDISCOVER messages the server has received.
• DHCP REQUEST: The number of DHCPREQUEST messages the server has received.
• DHCP DECLINE: The number of DHCPDECLINE messages the server has received.
• DHCP RELEASE: The number of DHCPRELEASE messages the server has received.
• DHCP INFORM: The number of DHCPINFORM messages the server has received.

Message Sent:

• DHCP OFFER: The number of DHCPOFFER messages the server sent.
• DHCP ACK: The number of DHCPACK messages the server sent.
• DHCP NACK: The number of DHCPNACK messages the server sent.

show ip dhcp conflict

This command displays address conflicts logged by the DHCP Server. If no IP address is specified, all the conflicting addresses are displayed.

• Format: show ip dhcp conflict [<ip-address>]
• Modes: Privileged EXEC/ User EXEC

The display parameters for above command are:

• IP address: The IP address of the host as recorded on the DHCP server.
• Detection Method: The manner in which the IP address of the hosts were found on the DHCP Server
• Detection time: The time when the conflict was found.