DHCP

The DHCP provides a framework for passing configuration information to hosts on a TCP/IP network.

DHCP utilizes a server/client model to deliver the protocol. DHCP servers allocate network addresses to clients and provide them with network configurations.

DHCP Server

Soodar uses Kea DHCP as a backend to provide DHCP server functionalities. These functionalities include:

Add IP pools and define subnet and ip ranges to allocate to hosts
Provide clients DNS server addresses
Provide clients gateway address
Provide clients NTP server addresses
Set leasing time for each pool
Show/Clear bindings

Configuring Pool

[no] ip dhcp pool DHCP4POOL

Create a new DHCP4 pool. Each pool has a subnet. This subnet determines which pool should be used for incoming requests by matchin pool subnet with ingress interface subent. The negate form, removes a pool from pools.

soodar(config)# ip dhcp pool p1
soodar(dhcp-config)#

[no] network A.B.C.D/M

Set pool’s subnet address.

soodar(config)# ip dhcp pool p1
soodar(dhcp-config)# network 192.168.1.0/24

[no] included-address A.B.C.D A.B.C.D

Define a range of addresses that could be used for allocating to clients from subnet. Each pool can have multiple included-address command.

soodar(config)# ip dhcp pool p1
soodar(dhcp-config)# included-address 192.168.1.100 192.168.1.120
soodar(dhcp-config)# included-address 192.168.1.140 192.168.1.165

[no] dns-server A.B.C.D ...

Configure DNS server address(es) that is fed to clients. User can provide all addresses in one command or issue multiple commands.

Note

Up to 8 DNS server can be set. It is not allowed to set more than 8 servers.

Example:

Following lines set 1.1.1.1, 4.2.2.4 and 8.8.8.8 as DNS servers:

soodar(config)# ip dhcp pool p1
soodar(dhcp-config)# dns-server 4.2.2.4 1.1.1.1
soodar(dhcp-config)# dns-server 8.8.8.8

[no] default-router A.B.C.D ...

Set gateway address(es) for presenting to clients. User can provide all addresses in one command or issue multiple commands.

Note

Up to 8 gateway can be set. It is not allowed to set more than 8 addresses.

soodar(config)# ip dhcp pool p1
soodar(dhcp-config)# default-router 192.168.1.1

[no] ntp-server NTP ...

Configure NTP server address(es) that is fed to clients. User can provide all addresses in one command or issue multiple commands.

Note

Up to 8 NTP server can be set. It is not allowed to set more than 8 servers.

soodar(config)# ip dhcp pool p1
soodar(dhcp-config)# ntp-server ir.pool.ntp.org

[no] domain-name NAME

Specifies the domain name for clients

soodar(config)# ip dhcp pool p1
soodar(dhcp-config)# domain-name example.org

[no] lease <(0-365) (0-23) (0-59)|infinite>

Set DHCP lease time in days, hours and minutes or infinite to disable lease time. Default lease time is 24 hours( 1 day). Negating resets lease time to default value.

soodar(config)# ip dhcp pool p1
soodar(dhcp-config)# ! set lease time to 30 days
soodar(dhcp-config)# lease 30 0 0

Configure interfaces

[no] ip dhcp server

Enable DHCP serving on interface. Negation disables DHCP serving.

soodar(config-if)# ip dhcp server

Pool status and management

show ip dhcp pool

Show general information about pool(s)

soodar# show ip dhcp pool p1

Pool p1 :
 Total addresses: 47
 Leased addresses:        1
 Declined addresses:      0
 2 ranges are currently in the pool :
 Range's low       Range's high
 192.168.1.100     192.168.1.120
 192.168.1.140     192.168.1.165

show ip dhcp binding [<DHCP4POOL|A.B.C.D>]

Show information about current bindings.

soodar# show ip dhcp binding
  IP Address   Client hostname   Client HW address   Lease expiration           Pool   Type        State
  1.1.1.100    n4                00:00:00:aa:00:01   Wed Nov  3 11:20:06 2021   p2     Automatic   Leased

clear ip dhcp binding <*|A.B.C.D>: Removes a binding from lease database. If * is the input argument, clears all bindings