Understanding How Bootp And Rarp Work - Cisco WS-X6066-SLB-APC - Content Switching Module Software Manual

Chapter 3 Configuring the Switch IP Address and Default Gateway
In addition to the sc0 interface IP address, the switch can obtain the subnet mask, broadcast address, and
default gateway address. DHCP-learned values are not used if user-configured values are present.
The switch broadcasts a DHCPDISCOVER message one to ten seconds after all of the switch ports are
online. The switch always requests an infinite lease time in the DHCPDISCOVER message.
If a DHCP or Bootstrap Protocol (BOOTP) server responds to the request, the switch takes appropriate
action. If a DHCPOFFER message is received from a DCHP server, the switch processes all supported
options contained in the message.
in the DHCPOFFER message are ignored.
Table 3-1
Code
1
2
3
6
12
15
28
33
42
51
52
61
66
If a BOOTP response is received from a BOOTP server, the switch sets the in-band (sc0) interface IP
address to the address specified in the BOOTP response.
If no DHCPOFFER message or BOOTP response is received in reply, the switch rebroadcasts the
request using an exponential backoff algorithm (the amount of time between requests increases
exponentially). If no response is received after ten minutes, the sc0 interface IP address remains set to
0.0.0.0 (provided that BOOTP and RARP requests fail as well).
If you reset or power cycle a switch with a DHCP- or BOOTP-obtained IP address, the information
learned from DHCP or BOOTP is retained. At bootup, the switch attempts to renew the lease on the IP
address. If no reply is received, the switch retains the current IP address.

Understanding How BOOTP and RARP Work

With BOOTP and RARP, you map the switch MAC address to an IP address on the BOOTP or RARP
server. The switch retrieves its IP address from the server automatically when it boots up.
The switch broadcasts 10 BOOTP and RARP requests after all of the switch ports are online. If a
response is received, the switch sets the in-band (sc0) interface IP address to the address specified in the
response.
78-13315-02
Table 3-1
Supported DHCP Options
Option
Subnet mask
Time offset
Router
Domain name server
Host name
Domain name
Broadcast address
Static route
NTP servers
IP address lease time
Option overload
Client-identifier
TFTP server name
Catalyst 6000 Family Software Configuration Guide—Releases 6.3 and 6.4
Understanding Automatic IP Configuration
shows the supported DHCP options. Other options specified
3-3