CCNA Cisco Certified Network Associate Study Guide - FTP Server

Introduction to Novell IPX 391
Please don’t confuse RIP in IPX with RIP in TCP/IP. They’re both routing protocols,
but they’re not the same routing protocol.
Service Advertising Protocol
NetWare servers use SAP to advertise the services they offer by sending out
an SAP broadcast every 60 seconds. The broadcast includes all services that
the server has learned about from other servers—not just the ones they furnish.
All servers receiving the SAP broadcast incorporate the information
into their own SAP tables; they then rebroadcast the SAP entries in their own
SAP updates. Because SAP information is shared among all servers, all servers
eventually become aware of all available services and are thereby
equipped to respond to client GNS requests. As new services are introduced,
they’re added to SAP tables on local servers and are rebroadcast until every
server knows they exist and knows where to get them.
So how does a Cisco router fit in here? Well, as far as SAP is concerned, the
Cisco router acts just like another NetWare server. By default, an SAP broadcast
won’t cross a Cisco router. A Cisco router catalogs all SAPs heard on any
of its IPX-enabled interfaces into its SAP table; unless you change the settings,
the router then broadcasts the whole table from each of those interfaces at 60second
intervals (just as a NetWare server does). This is an important point,
especially with WAN links. The router isolates SAP broadcasts to individual
segments and passes along only the summarized information to each segment.
Let’s take a look at an SAP broadcast with the Etherpeek analyzer.
Flags: 0x00
Status: 0x00
Packet Length:306
Timestamp: 23:48:36.362000 06/28/1998
Ethernet Header
Destination: ff:ff:ff:ff:ff:ff Ethernet Brdcast
Source: 00:80:5f:ad:14:e4
Protocol Type:81-37 NetWare
IPX - NetWare Protocol
Checksum: 0xffff
Length: 288