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"BOOTP Relay Agent" Feature Availability on the AT-9800 and SwitchBlade® Series Switches

"BOOTP Relay Agent" feature availability on SwitchBlade and AT-9800 Series

BOOTP is a UDP-based protocol which allows a booting host to configure itself dynamically without external interventions. A BOOTP server responds to requests from BOOTP clients for configuration information, such as the IP address the client should use. BOOTP is defined in RFC 951, “Bootstrap Protocol (BOOTP)”.

RFC 1542, “Clarifications and Extensions for the Bootstrap Protocol”, defines extensions to the BOOTP protocol, including the behavior of a BOOTP Relay Agent. The Router’s BOOTP Relay Agent relays BOOTREQUEST messages originating from any of the Router’s interfaces to a user-defined destination, and relays BOOTREPLY messages addressed to BOOTP clients on networks directly connected to the Router. BOOTREPLY messages addressed to clients on networks not directly connected to the Router are ignored by the relay agent and treated as ordinary IP packets for forwarding. A BOOTREQUEST message may be relayed via unicast, multicast or broadcast methods. In the last case, the message will not be re-broadcast to the interface 68 BOOTP Relay Agent Release Note from which it was received. The relay destinations are configured independently of other broadcast forwarders’ destinations (e.g. TFTP).

The ‘hops’ field in a BOOTP message is used to record the number of hops (Routers) the message has been through. If the value of the ‘hops’ field exceeds a predefined threshold (normally 16), the message will be discarded by the relay agent. The threshold may be set to a value in the range 1 to 16.

The BOOTP Relay Agent is enabled with the command:


The agent must currently be disabled. The agent can be disabled with the command:


A relay destination is defined with the command:


where ipadd is the IP address of a BOOTP server in dotted decimal notation. More than one relay destination may be defined, with successive commands. Request messages will be relayed to all defined relay destinations, so messages may be duplicated.

A relay destination may be deleted using the command:


where ipadd is the IP address of a BOOTP server in dotted decimal notation.

The destination must exactly match a destination previously defined with the

ADD BOOTP RELAY Command BOOTP configuration (including the relay destination list) can be purged

with the command:


The BOOTP module is disabled, all configuration data (including nonvolatile storage) is purged, and then BOOTP is re-enabled with default settings. When the ‘hops’ field in a BOOTP message exceeds a predefined threshold the BOOTP message is discarded. The default value of the threshold is 4. The threshold may be set to any value in the range 1 to 16 using the MAXHOPS parameter in the command:


The command:


displays the current configuration of the BOOTP Relay Agent.
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