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 MAC address of the switch. (To determine the switch’s MAC address, see Appendix D, "MAC Address Management". The switch properly handles replies from either type of server. If multiple replies are returned, the switch tries to use the first reply.)

N o t e

If you manually configure a gateway on the switch, it will ignore any gateway

 

address received via DHCP or Bootp.

 

If the switch is initially configured for DHCP/Bootp operation (the default),

 

 

or if it is rebooted with this configuration, it immediately 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 frequency. 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. 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".)

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