DHCP IP Per-Port HowTo
Introduction
This document shows how to set up the DHCP server to hand out a static IP address (lease) to clients connected to a specific physical port.
.---------------------.
| Switch | DHCP Server/Relay
| | iface: vlan1
| eth1 eth2 | 192.168.1.0/24
'--+---------------+--'
|.132 |.55
| |
.--+--. .--+--.
| H1 | | H2 |
'-----' '-----'
Figure 1: DHCP server setup with IP-per-port for port eth2.
In the case depicted above, clients connected to port eth1 receive an
address from the server's pool of addresses. Clients on port eth2 on
the other hand always receive a specific address, 192.168.1.55. Hence,
the most obvious use-case for the latter is to have a single end-device
connected to eth2.
For more information about any of the sub-systems used and their configurations options, see:
Configuration
Configuration of both DHCP server and DHCP relay services. First, we set
up the relay to forward all DHCP traffic to the local DHCP server. The
key setting is option82, which makes sure the relay agent appends DHCP
Option 82 port information for the server:
example:/#> configure
example:/config/#> dhcp-relay
example:/config/dhcp-relay/#> server 127.0.0.1
example:/config/dhcp-relay/#> iface vlan1
example:/config/dhcp-relay/iface-vlan1/#> port eth2
example:/config/dhcp-relay/iface-vlan1/port-eth2/#> circuitid-type portname
example:/config/dhcp-relay/iface-vlan1/port-eth2/#> end
example:/config/dhcp-relay/iface-vlan1/#> end
example:/config/dhcp-relay/#> option82
Activating Option 82.
example:/config/dhcp-relay/option82/#> remoteid-type mac
example:/config/dhcp-relay/option82/#> end
example:/config/dhcp-relay/#> end
example:/config/#>We can now move to set up the DHCP server, starting with the default subnet and address pool.
example:/config/#> dhcp-server
example:/config/dhcp-server/#> subnet 192.168.1.0/24
Created new DHCP server for subnet 192.168.1.0.
example:/config/dhcp-server/subnet-192.168.1.0/#> pool 192.168.1.100 100
example:/config/dhcp-server/subnet-192.168.1.0/#> end
example:/config/dhcp-server/#>Next, we set up the static lease for host(s) connected to port eth2.
The match option82 configuration is what the server use to identify
the correct port (circuit-id) and its own MAC address for iface vlan1
(remote-id).
example:/config/dhcp-server/#> host
example:/config/dhcp-server/host-1/#> match option82 circuit-id string eth2
example:/config/dhcp-server/host-1/#> match option82 remoteid-id string 0c:50:e5:65:97:00
example:/config/dhcp-server/host-1/#> address 192.168.1.55
example:/config/dhcp-server/host-1/#> end
example:/config/dhcp-server/#> leave
example:/#>Status
To verify that addresses are distributed as intended any provided lease can be viewed on the server:
example:/#> show dhcp-clients
LEASE TIME MAC ADDRESS CLIENT ID IP ADDRESS HOSTNAME
864000 0c:50:e5:07:24:00 01:0c:50:e5:07:24:00 192.168.1.132 H1
864000 0c:50:e5:65:97:00 01:0c:50:e5:65:97:00 192.168.1.55 H2