User`s guide

®
USER’S GUIDE AUTOMATIC TRANSFER SWITCH
110
DHCP & BOOTP boot process
When Boot mode is set to its default DHCP & BOOTP setting, the
following occurs when the Automatic Transfer Switch is started or reset:
1. The Automatic Transfer Switch makes up to five requests for its
network assignment from any BOOTP server. If a valid BOOTP
response is received, the Automatic Transfer Switch starts the network
services and sets Boot mode to BOOTP Only.
2. If the Automatic Transfer Switch fails to receive a valid BOOTP
response after five BOOTP requests, the Automatic Transfer Switch
makes up to five requests for its network assignment from any DHCP
server. If a valid DHCP response is received, the Automatic Transfer
Switch starts the network services and sets Boot mode to DHCP Only.
3. If the Automatic Transfer Switch fails to receive a valid DHCP response
after five DHCP requests, it repeats BOOTP and DHCP requests until
it receives a valid network assignment. First it sends a BOOTP request
every 32 seconds for 12 minutes, then it sends one DHCP request with
a time-out of 64 seconds, and so forth.
To configure the Automatic Transfer Switch so that it always
uses the DHCP & BOOTP setting for Boot mode, enable
the Remain in DHCP & BOOTP mode after accepting
TCP/IP settings option, which is disabled by default.
If a DHCP server responds with an invalid offer (i.e., without
the APC cookie), the Automatic Transfer Switch accepts the
lease from that server on the last request of the sequence and
immediately releases that lease. This prevents the DHCP
server from reserving the IP Address associated with its
invalid offer.
For more information on what a valid response requires, see
DHCP response options.