Configuring IP Addressing

IP Configuration

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. Depending on how the DHCP server is configured, the switch may receive an IP address that 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 D, “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 many Unix systems, the Bootp database is contained in the /etc/bootptab file. In contrast to DHCP operation, Bootp configurations are always the same for a specific 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:

2520switch:\

ht=ether:\

ha=0030c1123456:\

ip=10.66.77.88:\

sm=255.255.248.0:\

gw=10.66.77.1:\

hn:\

vm=rfc1048

An entry in the Bootp table file /etc/bootptab to tell the switch or VLAN where to obtain a configuration file download would be similar to this entry:

2520switch:\

ht=ether:\

ha=0030c1123456:\

ip=10.66.77.88:\

sm=255.255.248.0:\

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