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Configuring IP Addressing
IP Configuration
The DHCP/Bootp Process. Whenever the IP Config parameter in the switch
or in an individual VLAN in the switch is configured to DHCP/Bootp (the
default), or when the switch is rebooted with this configuration:
1. DHCP/Bootp requests are automatically broadcast on the local network.
(The switch sends one type of request to which either a DHCP or Bootp
server can respond.)
2. When a DHCP or Bootp server receives the request, it replies with a
previously configured IP address and subnet mask for the switch. The
switch also receives an IP Gateway address if the server has been config-
ured to provide one. In the case of Bootp, the server must first be
configured with an entry that has the switch’s MAC address. (To determine
the switch’s MAC address, refer to Appendix D, “MAC Address Manage-
ment”.) The switch properly handles replies from either type of server. If
multiple replies are returned, the switch tries to use the first reply.)
Note If you manually configure default gateway, TTL, TimeP, and/or SNTP param-
eters on the switch, it ignores any values received for the same parameters via
DHCP or Bootp.
If the switch is initially configured for DHCP/Bootp operation (the default),
or if it reboots with this configuration, it begins sending request packets on
the network. If the switch does not receive a reply to its DHCP/Bootp requests,
it continues to periodically send request packets, but with decreasing fre-
quency. Thus, if a DHCP or Bootp server is not available or accessible to the
switch when DHCP/Bootp is first configured, the switch may not immediately
receive the desired configuration. After verifying that the server has become
accessible to the switch, reboot the switch to re-start the process immediately.
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.
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