Technical data
BLADE OS 5.1 Application Guide
18
Chapter 1: Accessing the Switch BMD00136, November 2009
BOOTP Relay Agent Configuration
To enable the G8000 to be the BOOTP forwarder, you need to configure the BOOTP server IP
addresses on the switch, and enable BOOTP relay on the interface(s) on which the BOOTP requests
are received.
Generally, you should configure the command on the switch IP interface that is closest to the client,
so that the BOOTP server knows from which IP subnet the newly allocated IP address should come.
Use the following commands to configure the switch as a BOOTP relay agent:
Use the following command to enable the Relay functionality on an IP interface:
DHCP Relay Agent
DHCP Relay Agent Overview
DHCP is described in RFC 2131, and the DHCP relay agent supported on the G8000 is described in
RFC 1542. DHCP uses UDP as its transport protocol. The client sends messages to the server on
port 67 and the server sends messages to the client on port 68.
DHCP defines the methods through which clients can be assigned an IP address for a finite lease
period and allowing reassignment of the IP address to another client later. Additionally, DHCP
provides the mechanism for a client to gather other IP configuration parameters it needs to operate
in the TCP/IP network.
In the DHCP environment, the switch acts as a relay agent. The DHCP relay feature enables the
switch to forward a client request for an IP address to two BOOTP servers with IP addresses that
have been configured on the switch.
When a switch receives a UDP broadcast on port 67 from a DHCP client requesting an IP address,
the switch acts as a proxy for the client, replacing the client source IP (SIP) and destination IP (DIP)
addresses. The request is then forwarded as a UDP Unicast MAC layer message to two BOOTP
servers whose IP addresses are configured on the switch. The servers respond as a a UDP Unicast
message back to the switch, with the default gateway and IP address for the client. The destination
IP address in the server response represents the interface address on the switch that received the
client request. This interface address tells the switch on which VLAN to send the server response to
the client.
>> # ip bootp-relay server1 <IP address>
>> # ip bootp-relay server2 <IP address>
>> # ip bootp-relay enable
>> # interface ip <interface number>
>> (config-ip-if)# relay