Cisco 7604 Configuration Manual page 182

Configuring DHCP
Where the vlan vlan_id or mapped_interface argument is the interface on which you want to enable
DHCP relay.
You can enter the dhcprelay server command up to 4 times per interface, with a maximum of 10
servers allowed (including global servers) per context or in single mode.
The interface-specific servers take precedence over any global servers configured.
The DHCP servers cannot reside on the same interface on which you enable DHCP relay. (The
FWSM determines which interface is connected to the DHCP server by using the routing table.)
Note
• To configure a global server, enter the following command:
hostname(config)# dhcprelay server ip_address if_name
Where the if_name argument is the interface connected to the DHCP server. The DHCP server must
reside on a different interface from the DHCP clients where you enable DHCP relay.
You can use this command up to 10 times to identify up to 10 servers, including any
interface-specific servers.
To enable DHCP relay on the interface connected to the clients, enter the following command:
Step 2
hostname(config)# dhcprelay enable interface
You can enable DHCP relay on multiple interfaces; however, you cannot configure DHCP relay on any
interfaces that are connected to the DHCP servers. For example, you can configure DHCP relay on
inside1 and inside 2 interfaces, and configure DHCP servers on outside and dmz interfaces. You cannot
configure any servers on inside1 or inside2.
(Optional) To set the number of seconds allowed for relay address negotiation, enter the following
Step 3
command:
hostname(config)# dhcprelay timeout seconds
(Optional) To change the first default router address in the packet sent from the DHCP server to the
Step 4
address of the FWSM interface, enter the following command:
hostname(config)# dhcprelay setroute if_name
This action allows the client to set its default route to point to the FWSM even if the DHCP server
specifies a different router.
If there is no default router option in the packet, the FWSM adds one containing the interface address.
The following example enables the FWSM to forward DHCP requests from clients connected to the
inside1 and inside2 interfaces to a global DHCP server on the outside interface and a global DHCP server
on the DMZ interface:
hostname(config)# dhcprelay server 209.165.200.225 outside
hostname(config)# dhcprelay server 209.165.201.4 dmz
hostname(config)# dhcprelay enable inside1
hostname(config)# dhcprelay setroute inside1
hostname(config)# dhcprelay enable inside2
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide using ASDM
8-40
If you configure an interface-specific server address after a connection has already been set up
between a client and an existing global DHCP server, the client keeps using the global server
until the server address lease expires. After the lease expires, new connections use the
interface-specific server.
Chapter 8 Configuring IP Routing and DHCP Services
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