Understanding Automatic Ip Configuration; Automatic Ip Configuration Overview; Understanding How Dhcp Works - Cisco WS-X6066-SLB-APC - Content Switching Module Software Manual

Understanding Automatic IP Configuration

When you configure the IP address, subnet mask, broadcast address, and VLAN membership of the sc0
interface, you can access the switch through Telnet or Simple Network Management Protocol (SNMP).
When you configure the SLIP (sl0) interface, you can open a point-to-point connection to the switch
through the console port from a workstation.
All IP traffic generated by the switch itself (for example, a Telnet session opened from the switch to a
host) is forwarded according to the entries in the switch IP routing table. For intersubnetwork
communication to occur, you must configure at least one default gateway for the sc0 interface. The
switch IP routing table is used to forward traffic originating on the switch only, not for forwarding traffic
sent by devices connected to the switch.
Understanding Automatic IP Configuration
These sections describe how the switch can obtain its IP configuration automatically:
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Automatic IP Configuration Overview

The switch can obtain its IP configuration automatically using one of the following protocols:
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The switch makes BOOTP, DHCP, and RARP requests only if the sc0 interface IP address is set to
0.0.0.0 when the switch boots up. This address is the default for a new switch or a switch whose
configuration file has been cleared using the clear config all command. BOOTP, DHCP, and RARP
requests are only broadcast out the sc0 interface.
If the CONFIG_FILE environment variable is set, all configuration files are processed before the
Note
switch determines whether to broadcast BOOTP, DHCP, and RARP requests. For more information
about the CONFIG_FILE environment variable, see
Configuration."

Understanding How DHCP Works

There are three methods for obtaining an IP address from the DHCP server:
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Catalyst 6000 Family Software Configuration Guide—Releases 6.3 and 6.4
3-2
Automatic IP Configuration Overview, page 3-2
Understanding How DHCP Works, page 3-2
Understanding How BOOTP and RARP Work, page 3-3
Bootstrap Protocol (BOOTP)
Dynamic Host Configuration Protocol (DHCP)
Reverse Address Resolution Protocol (RARP)
Manual allocation—The network administrator maps the switch MAC address to an IP address at
the DHCP server.
Automatic allocation—The switch obtains an IP address when it first contacts the DHCP server. The
address is permanently assigned to the switch.
Dynamic allocation—The switch obtains a "leased" IP address for a specified period of time. The
IP address is revoked at the end of this period, and the switch surrenders the address. The switch
must request another IP address.
Chapter 3 Configuring the Switch IP Address and Default Gateway
Chapter 23, "Modifying the Switch Boot
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