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Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide using ASDM
OL-20748-01
Chapter 8 Configuring IP Routing and DHCP Services
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
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.
•
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.
Step 2
To enable DHCP relay on the interface connected to the clients, enter the following command:
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.
Step 3
(Optional) To set the number of seconds allowed for relay address negotiation, enter the following
command:
hostname(config)#
dhcprelay timeout
seconds
Step 4
(Optional) To change the first default router address in the packet sent from the DHCP server to the
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
Summary of Contents for 6500 - Catalyst Series 10 Gigabit EN Interface Module Expansion
Page 35: ...P A R T 1 Getting Started and General Information ...
Page 36: ......
Page 297: ...P A R T 2 Configuring the Security Policy ...
Page 298: ......
Page 521: ...P A R T 3 System Administration ...
Page 522: ......
Page 613: ...P A R T 4 Reference ...
Page 614: ......