To use the DHCP server of the local router to assign IP addresses to the
hosts that are connected to the LAN interface of the router, a pool of IP
addresses must be created for the internal DHCP server
. The DHCP server
then assigns an IP address from this pool to each host when it connects to the
router.
In a typical VPN connection, the hosts connected to the LAN interface of the
router are assigned an IP address in a private address space. The router then
uses NAT/PAT to translate those IP addresses into a single IP address that is
transmitted across the VPN tunnel connection.
The following steps are
used to create the DHCP server pool:
Step 1
Create a DHCP
server address pool using the ip dhcp pool pool-name
command. This places the administrator in DHCP pool configuration
mode.
Step 2
Use the network command to
specify the IP network and subnet mask of the address pool that will be used by
the hosts connected to the local Ethernet interface of the router.
Step 3
Use the default-router command to
specify the IP address of the default router for a DHCP client. At least one
address must be specified. Up to eight addresses can be specified per
command.
Step 4
Use the import all command
to ensure that the router is configured with the proper DHCP parameters from
the central DHCP server. This option requires a central DHCP server be
configured to provide the DHCP options. This server can be on a different
subnet or network.
Step 5
The lease
command is optional. Use this command to specify the duration of the DHCP
lease. Use the exit command to leave the DHCP pool
configuration mode.
Step 6
Use the ip dhcp
excluded-address command to exclude the specified address from the
DHCP server pool. The lan-ip-address should be the IP
address assigned to the LAN interface of the router.
One example of a
DHCP server pool configuration is shown in Figure
.