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.)

N o t e

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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