Ospf Implementation; Defining Areas - Radware Alteon Application Manual

OSPF Implementation

Alteon supports a single instance of OSPF and up to 4 K routes on the network. The following
sections describe Alteon OSPF implementation:
• Defining Areas, page 141
• Interface Cost, page 143
• Electing the Designated Router and Backup, page 143
• Summarizing Routes, page 143
• Default Routes, page 143
• Virtual Links, page 145
• Router ID, page 145
• Authentication, page 146
• Host Routes for Load Balancing, page 148
• Redistributing Routes into OSPF, page 148

Defining Areas

If you are configuring multiple areas in your OSPF domain, one of the areas must be designated as
area 0, known as the backbone. The backbone is the central OSPF area and is usually physically
connected to all other areas. The areas inject routing information into the backbone which, in turn,
disseminates the information into other areas.
Since the backbone connects the areas in your network, it must be a contiguous area. If the
backbone is partitioned (possibly as a result of joining separate OSPF networks), parts of the AS will
be unreachable, and you will need to configure virtual links to reconnect the partitioned areas (see
Virtual Links, page 145).
Up to three OSPF areas can be connected to Alteon. To configure an area, the OSPF number must be
defined and then attached to a network interface on Alteon. The full process is explained in this
section.
An OSPF area is defined by assigning two pieces of information—an area index and an area ID. The
command to define an OSPF area is as follows:
>> # /cfg/l3/ospf/aindex <area index> /areaid <n.n.n.n>
Note: The aindex option is an arbitrary index used only by Alteon, and does not represent the
actual OSPF area number. The actual OSPF area number is defined in the
command.
Assigning the Area Index
The
aindex <area index>
does not necessarily represent the OSPF area number, though for configuration simplicity, it should
where possible.
For example, both of the following sets of commands define OSPF area 0 (the backbone) and area 1
because that information is held in the area ID portion of the command. However, the first set of
commands is easier to maintain because the arbitrary area indexes agree with the area IDs:
• Area index and area ID agree
Document ID: RDWR-ALOS-V2900_AG1302
Alteon Application Switch Operating System Application Guide
option is an arbitrary index (0 to 2) used only by Alteon. This index
Open Shortest Path First (OSPF)
portion of the
areaid
141