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Cisco Catalyst Blade Switch 3130 for Dell Software Configuration Guide
OL-13270-01
Chapter3 Assigning the Switch IP Address and Default Gateway Assigning Switch Information
Configuring the Relay Device
You must configure a relay device, also referred to as a relay agen t , wh en a sw itc h send s b roa dcas t
packets that require a response from a host on a different LAN. Examples of broadcast packets that the
switch might send are DHCP, DNS, and in some cases, TFTP packets. You must configure this relay
device to forward received broadcast packets on an interface to the destination host.
If the relay device is a Cisco router, enable IP routing (ip routing global configuration command), an d
configure helper addresses by using the ip helper-address interface configuration command.
For example, in Figure 3-2, configure the router interfaces as follows:
On interface 10.0.0.2:
router(config-if)# ip helper-address 20.0.0.2
router(config-if)# ip helper-address 20.0.0.3
router(config-if)# ip helper-address 20.0.0.4
On interface 20.0.0.1
router(config-if)# ip helper-address 10.0.0.1
Note If the switch is acting as the relay device, configure the interface as a routed po rt. F or mor e informa tion,
see the “Routed Ports” section on page 10-4 and the “Configuring Layer 3 Inte rfaces” section on
page 10-22.
Figure3-2 Relay Device Used in Autoconfiguration
Obtaining Configuration Files
Depending on the availability of the IP address and the configuration filename in the DHCP reserved
lease, the switch obtains its configuration information in these ways:
The IP address and the configuration filename is reserved fo r th e s witc h an d pr ovided in the DHCP
reply (one-file read method).
The switch receives its IP address, subnet mask, TFTP server address, an d the configur ation
filename from the DHCP server. The switch sends a unicast message to the TFTP server to retrieve
the named configuration file from the base directory of the server and upon rec eipt, it completes its
boot up process.
Switch
(DHCP client) Cisco router
(Relay)
49068
D
HCP server TFTP server DNS server
20.0.0.2 20.0.0.3
20.0.0.1
10.0.0.2
10.0.0.1
20.0.0.4