Routers B
and C will each get it there.
Which route is best?
B A
D C
EIGRP
Administrative
Distance = 90
RIP
Administrative
Distance = 120
E
Enabling RIP 399
When a classful routing protocol is used, all subnetworks of the same major network (Class
A, B, or C) must use the same subnet mask. Routers that are running a classful routing
protocol perform automatic route summarization across network boundaries.
Upon receiving a routing update packet, a router that is running a classful routing protocol
takes one of the following actions to determine the network portion of the route:
?– If the routing update information contains the same major network number as is
con?¬?gured on the receiving interface, the router applies the subnet mask that is
con?¬?gured on the receiving interface.
?– If the routing update information contains a major network that is different from that
con?¬?gured on the receiving interface, the router applies the default classful mask (by
address class) as follows:
??” For Class A addresses, the default classful mask is 255.0.0.0.
??” For Class B addresses, the default classful mask is 255.255.0.0.
??” For Class C addresses, the default classful mask is 255.255.255.0.
RIP version 2 is a classless routing protocol.
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