IP R
OUTING
3-295
Configuring Area Ranges
(Route Summarization for ABRs)
An OSPF area can include a large number of
nodes. If the Area Border Router (ABR) has
to advertise route information for each of
these nodes, this wastes a lot of bandwidth
and processor time. Instead, you can
configure an ABR to advertise a single summary route that covers all the
individual networks within its area. When using route summaries, local
changes do not have to be propagated to other area routers. This allows
OSPF to be easily scaled for larger networks, and provides a more stable
network topology.
Command Usage
•
Use the Area Range Configuration page to summarize the routes for
an area. The summary route for an area is defined by an IP address and
network mask. You therefore need to structure each area with a
contiguous set of addresses so that all routes in the area fall within an
easily specified range. This router also supports Variable Length
Subnet Masks (VLSMs), so you can summarize an address range on
any bit boundary in a network address.
•
To summarize the external LSAs imported into your autonomous
system (i.e., local routing domain), use the Summary Address
Configuration screen (page 3-308).
Console#
show ip ospf
3-170
Routing Process with ID 192.168.1.253
Supports only single TOS(TOS0) route
Number of area in this router is 3
Area 0.0.0.0 (BACKBONE)
Number of interfaces in this area is 1
SPF algorithm executed 40 times
Area 0.0.0.2 (STUB)
Number of interfaces in this area is 1
SPF algorithm executed 8 times
Area 0.0.0.3 (NSSA)
Number of interfaces in this area is 1
SPF algorithm executed 40 times
Console#
area
area
ABR
summary
route
Summary of Contents for 8612XL3
Page 2: ......
Page 26: ...CONTENTS xxvi ...
Page 40: ...INTRODUCTION 1 14 ...
Page 69: ...BASIC CONFIGURATION 3 15 ...
Page 175: ...PORT CONFIGURATION 3 121 ...
Page 337: ...IP ROUTING 3 283 Web Click Routing Protocol RIP Statistics ...
Page 379: ...MULTICAST ROUTING 3 325 Command Usage ...
Page 396: ...CONFIGURING THE SWITCH 3 342 ...
Page 582: ...COMMAND LINE INTERFACE 4 186 ...
Page 806: ... 224 Command Mode Privileged Exec Example Console clear vrrp 1 interface 1 counters Console ...
Page 826: ... 6 ...
Page 828: ...TROUBLESHOOTING B 2 ...
Page 838: ...GLOSSARY Glossary 10 ...
Page 845: ......