HP ProCurve Secure Router 7203 dl Advanced Management And Configuration Manual page 639

With route summarization, an interface can broadcast:
Destination IP Address
10.0.0.0 255.0.0.0
Route summarization is particularly useful for limiting the amount of band-
width routers consume with RIP updates. It also limits the memory the routing
table occupies.
If you are using RIP version 1 or you have enabled auto-summary, RIP
summarizes routes whenever they are advertised across network boundaries.
For example, Router A in Figure 13-4 can advertise network 10.0.0.0 /8 to
Router B rather than networks 10.1.1.0 /24 and 10.1.2.0 /24, because Router A
and B connect through a subnet on a different classful network (1.1.1.0 /30).
By default, route summarization is disabled. You can enable it by entering this
RIP configuration mode command:
ProCurve(config-rip)# auto-summary
RIP must always summarize up to the classful boundary. This can be a problem
for WANs using subnets in the same classful network at different sites. When
a WAN includes non-contiguous subnets, the same route will not be accurate
for each destination in the range of subnets.
Router A
Network 2
10.1.2.0 /24
Network 1
10.1.1.0 /24
Figure 13-4. Network That Cannot Use Route Summaries
IP Routing—Configuring RIP, OSPF, BGP, and PBR
Next-Hop IP address
10.1.1.1
WAN Connection
1.1.1.0 /30
Router B
Router C
Network 3
10.1.3.0 /24
Configuring RIP
Metric
1
Network 1 Next hop A
Network 2 Next hop A
Network 3 Next hop C
WAN Connection
2.2.2.0 /30
13-25