RIP
and SAP
Shivaź internetworking devices use RIP (Routing Information
Protocol) over IP, and RIP and SAP (Service Advertising
Protocol) over IPX* to exchange routing and service information
with other routers and to update the information in their
routing tables dynamically. A router refers to its routing
table to determine the next hop router to which data must
be sent to reach its destination.
A routing table might look like this, although the exact
format and contents vary from system to system:
Destination Router
85.0.0.0
Router_1
87.0.0.0 Router_2
If
RIP and SAP are disabled, routers at both sides of the WAN
must be statically configured with the information that
they would otherwise receive across the WAN in broadcast
RIP or SAP messages. This is very time-consuming for the
system administrator, as well as inefficient. Static routing
tables can quickly become out of date. Shiva recommends
that static routes or services be used on lines with low
bandwidth (<64K), or in cases where Triggered RIP and SAP
cannot be used.
There
are two types of RIP and SAP operation:
Standard RIP (version 1 and 2) and SAP
Triggered
RIP and SAP
Note:
Version 2 IP RIP packets contain information about the complete
route to be taken, including the subnet mask. There is no
Version 2 RIP for IPX.
Standard
RIP and SAP
When
RIP and SAP operate in the standard (or broadcast) way,
messages are sent regularly (every 60 seconds for IPX and
every 30 seconds for IP). This uses WAN bandwidth and causes
expensive, unnecessary calls on wide area networks. This
mode of operation is only recommended for high bandwidth
leased lines.
Triggered
RIP and SAP
Triggered
RIP and SAP dynamically updates routing information without
using excessive bandwidth. Update messages are sent when
the router detects a change in its routing or service database.
This means that routing and service data are only sent when
required, reducing WAN usage and costs, while still being
responsive to topology changes.
Shiva
recommends using triggered mode on lines with reasonable
bandwidth (>=64K). There is one note to this recommendation.
You can only run Triggered RIP and SAP to as many remote
sites as your physical interface can handle.
