Route Aggregation; Versus Rip-2 - 3Com corebuilder 3500 Implementation Manual

Route Aggregation

RIP-1 Versus RIP-2
Route aggregation mode determines which route table entries are sent
during a RIP-2 update:
If route aggregation mode is enabled, RIP-2 can function like RIP-1
and "collapse" route table entries for all subnets of a directly
connected network.
For example, if route aggregation is enabled, and the system is
advertising subnets 150.100.31.0 and 150.100.32.0, only the entry
for network 150.100.0.0 is sent in the update. With RIP Version 2, you
must enable route aggregation mode if you want the interface to
collapse the route table entries and function like RIP-1.
If route aggregation mode is
sends all routing table entries.
Like RIP-1, RIP-2 allows the system to dynamically configure its own
routing table. RIP-2 is much more flexible and efficient than RIP-1,
however, because RIP-2 advertises using the multicast method, which can
advertise to a subset of the network (RIP-1 uses the broadcast method,
which advertises to the whole network). RIP-2 can do this because it
includes a subnet mask in its header. (See Figure 59.)
If your system receives a RIP-2 packet, your system puts the route into the
routing table with the subnet mask that was advertised.
Figure 59 RIP-1 Versus RIP-2
How IP address 158.101.5.1
goes into the routing table of
System B:
RIP-1 158.101.0.0
RIP-2 158.101.5.0
Routing Information Protocol (RIP)
(the default), a RIP-2 update
disabled
158.101.5.1
(255.255.255.0)
System A
System B
299
Gateway address
158.101.1.254
(255.255.255.0)
Gateway address
158.101.1.253
(255.255.255.0)