Trigger Rip; Rip Startup And Operation - 3Com 3C13636 Configuration Manual

3Com Router 3000 Ethernet Family
Configuration Guide
Note:
RIP-2 supports both broadcasting and multicasting. By default, multicasting applies
and the IP multicast address is 224.0.0.9. When RIP-2 broadcasting is running on
interfaces, RIP-1 packets can also be received.

3.1.3 Trigger RIP

Trigger RIP (TRIP) is an extension of RIP on WAN circuits primarily for dial-up
networks.
TRIP removes periodic updating and includes retransmission and backup routing. It
adopts a new algorithm to test connectivity, ensuring that the route for a dial-up link is
retained even after the link is disconnected. TRIP allows the system to disconnect links
when the routing table is stable and no data is waiting for transmission. These links can
be set up when the routing table changes or when data needs transmission. This
greatly saves cost.
Instead of periodically broadcasting updates, TRIP sends updates only when triggered.
These updates are forwarded only when acknowelegement is received. This
decreases route management overheads. TRIP is suitable for dial-up networks and
networks implementing traffic-based accounting.
TRIP implementation of V 2.41 supports RFC2091, RFC2082, and simple and MD5
authentication of RFC2453.
TRIP supports route summary but not equal-cost routes.

3.1.4 RIP Startup and Operation

The whole process of RIPv1 startup and running can be described as follows:
When RIP is just enabled on a router, request packet is forwarded to a neighbor
router in broadcast mode. After the neighbor router receives the packet, it will
respond to the request and resend a response packet containing information in the
local routing table.
When the former router receives the response packet, it will modify its local routing
table and send a modification triggering packet to the neighbor router and
broadcast the route modification information. Upon receiving the modification
triggering packet, the neighbor router will send it to all its neighbor routers. After a
series of modification triggering broadcast, each router can get and keep the
updated routing information.
At the same time, RIP broadcasts its routing table to the adjacent routers every 30
seconds. The adjacent routers will maintain their own routing tables after receiving
the packets and will select an optimal route, and then advertise the modification
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Chapter 3 RIP Configuration