16th. BOOTP Bootstrap Protocol

16.5 BOOTP traversing Routers

we're in 5.4 section mentions RARP is that it uses link-layer broadcasts, which are typically not forwarded by the route ". This requires setting up a RARP server within each physical network. If the router supports BOOTP protocol, then BOOTP can be forwarded by the router (the majority of router vendors ' products support this feature).

This feature is primarily used for diskless routers, because if the multi-user system on disk is used as a router, it can run it yourself BOOTP   server. In addition, the commonly used Unix BOOTP server (appendix F ) supports this trunking mode

( relay mode). However, if you are running a BOOTP server within this physical network , it is usually not necessary to have BOOTP to another server in a different network.

Consider the router (also known as the " BOOTP Relay Agent ") well-known port on the server ( ) received BOOTP what happens when the request is requested. When you receive a BOOTP request, the relay Agent will have its IP address filled in received BOOTP Gateway in Request IP address field, and then sends the request to the true BOOTP server (by relay generation fill in the address of the Gateway field is received BOOTP Span style= "font-family:;" > request interface for IP address). The agent relay also skips the numeric field value plus 1

(This is to prevent requests from being forwarded indefinitely within the network.) RFC 951 thinks that if the hop value reaches 3 , the request can be discarded. Since the request is a unicast datagram (as opposed to the broadcast of the originating customer's request), it can follow a certain route through the other routers to reach the real BOOTP server. The real BOOTP server receives this request and produces a BOOTP response, and send it back to the relay agent instead of the requested customer. Since the Request Gateway field is not zero, the true BOOTP The server knows that the request was forwarded. The relay Agent receives an answer and sends it to the requested customer.

16.7 Summary

BOOTP Use UDP , which gets it for the boot diskless system IP address provides an exception to RARP a different option outside. BOOTP can also return other information, such as the of the router IP address, client's subnet mask, and name server IP address. since BOOTP for the system boot process, a diskless system requires the following protocols to be completed in read-only memory:

BOOTP , TFTP , UDP , IP and a local area network driver.

BOOTP servers are easier to implement than RARP servers because BOOTP requests and responses are UDP in the data report, Instead of a special data link layer frame. A router can also act as a proxy for a true BOOTP server, to a true BOOTP that resides in a different network The server forwards the client's BOOTP request.

16th. BOOTP Bootstrap Protocol