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Configuring the Switch
IP Configuration
Configuring the Switch
DHCP Operation. A significant difference between a DHCP configuration
and a Bootp configuration is that an IP address assignment from a DHCP
server is automatic, requiring no configuration of the DHCP server. Using that
automatic feature, though, the address is temporarily leased. Periodically the
switch may be required to renew its lease of the IP configuration. Thus, the IP
addressing provided by the server may be different each time the switch
reboots or renews its configuration from the server. However, you can fix the
address assignment for the switch by doing either of the following:
■ Configure the server to issue an “infinite” lease.
■ Using the switch’s MAC address as an identifier, configure the server with
a “Reservation” so that it will always assign the same IP address to the
switch. (For MAC address information, refer to appendix B, “MAC
Address Management”.)
For more information on either of these procedures, refer to the documenta-
tion provided with the DHCP server.
Bootp Operation. When a Bootp server receives a request it searches its
Bootp database for a record entry that matches the MAC address in the Bootp
request from the switch. If a match is found, the configuration data in the
associated database record is returned to the switch. For most Unix systems,
the Bootp database is contained in the /etc/bootptab file. In contrast to DHCP
operation, Bootp configurations are always the same for each receiving
device. That is, the Bootp server replies to a request with a configuration
previously stored in the server and designated for the requesting device.
Bootp Database Record Entries. A minimal entry in the Bootp table file
/etc/bootptab to update an IP address and subnet mask to the switch or a VLAN
configured in the switch would be similar to this entry:
j4121switch:\
ht=ether:\
ha=040009123456:\
ip=55.66.77.88:\
sm=255.255.248.0:\
gw=55.66.77.1:\
lg=11.22.33.44:\
hn:\
vm=rfc1048