3-7
Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 3 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 agent
, when a switch sends broadcast
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), and
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 port. For more information,
see the
“Routed Ports” section on page 11-4
and the
“Configuring Layer 3 Interfaces” section on
page 11-25
.
Figure 3-2
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 for the switch and provided in the DHCP
reply (one-file read method).
The switch receives its IP address, subnet mask, TFTP server address, and the configuration
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 receipt, it completes its
boot-up process.
Switch
(DHCP client)
Cisco router
(Relay)
49068
DHCP 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
Содержание 3750G - Catalyst Integrated Wireless LAN Controller
Страница 80: ...1 28 Catalyst 3750 Switch Software Configuration Guide OL 8550 02 Chapter 1 Overview Where to Go Next ...
Страница 606: ...27 8 Catalyst 3750 Switch Software Configuration Guide OL 8550 02 Chapter 27 Configuring UDLD Displaying UDLD Status ...
Страница 670: ...31 18 Catalyst 3750 Switch Software Configuration Guide OL 8550 02 Chapter 31 Configuring SNMP Displaying SNMP Status ...
Страница 1048: ...41 20 Catalyst 3750 Switch Software Configuration Guide OL 8550 02 Chapter 41 Configuring MSDP Monitoring and Maintaining MSDP ...
Страница 1086: ...43 26 Catalyst 3750 Switch Software Configuration Guide OL 8550 02 Chapter 43 Troubleshooting Using the crashinfo Files ...
Страница 1104: ...B 4 Catalyst 3750 Switch Software Configuration Guide OL 8550 02 Appendix B Supported MIBs Using FTP to Access the MIB Files ...