Cabletron Systems CSX100 series User Manual - Ip Routing

ISDN Router

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IP Routing

IP routing support provides the ability to process TCP/IP frames at the

network layer for routing.  IP routing support includes the Routing

Information Protocol (RIP) which allows the exchange of routing information

on a TCP/

IP network.  The router receives and broadcasts RIP messages to adjacent

routers and workstations.  Since IP sends out periodic RIP frames that could

keep dial-up links permanently connected, filtering and spoofing are

performed to minimize these broadcasts on the WAN links.  The router uses

the ‘piggyback method’ to send RIP update packets to the WAN port.  The

piggyback method means that RIP update packets are sent only when the dial-

up link is established because of data traffic.

IPX Routing

Internetwork Packet Exchange (IPX) Routing support provides the ability to

process IPX frames at the network layer.  This support includes the Routing

Information Protocol (RIP)* which allows the exchange of routing

information on an Internetwork, and the Service Advertising Protocol (SAP),

which provides a means of exchanging Internetwork service information. The

router receives and broadcasts RIP and SAP messages to adjacent routers and

workstations so that clients on the network can determine what services (file,

print, etc.) are available on the network and obtain the Internetwork address

of the servers.

Since IPX sends several types of control packets that could keep dial-up links

permanently connected, control of updates, and spoofing techniques are

employed to reduce this traffic.  Specifically, RIP, SAP, Watchdog, and

serialization frames are filtered and spoofed.  RIP and SAP update frames are

only sent piggybacked with data packets.  SAP requests for the nearest server

are spoofed, serialization frames are dropped, and Watchdog frames are

spoofed.

* IPX-RIP is similar to IP-RIP except IPX-RIP includes a time delay in

addition to a hop count