Ase Routes; Ospf Virtual Links - Avaya 8800 Configuration Manual

• An ASBR summary link advertisement describes the cost of the path to an ASBR from
the router that generates the advertisement.
• An ASE link advertisement is sent by an ASBR to describe the cost of the path to a
destination outside the AS from the ASBR generating the advertisement. This information
is flooded to all routers in the AS.

ASE routes

OSPF considers the following routes to be ASE routes:
• a route to a destination outside the AS
• a static route
• a default route
• a route derived by RIP
• a directly connected network not running OSPF

OSPF virtual links

On an OSPF network, an Ethernet Routing Switch 8800/8600 that acts as an ABR must
connect directly to the backbone. If no physical connection is available, you can automatically
or manually configure a virtual link.
An automatic virtual link can provide redundancy support for critical network connections.
Automatic virtual linking creates virtual paths for vital traffic paths in your OSPF network. If a
connection fails on the network, such as when an interface cable providing connection to the
backbone (either directly or indirectly) disconnects from the switch, the virtual link is available
to maintain connectivity.
Specify automatic virtual linking to ensure that a link is created to another router. When you
specify automatic virtual linking, this feature is always ready to create a virtual link. If automatic
virtual linking uses more resources than you want to expend, creating a manual virtual link can
be the better solution. Use this approach to conserve resources while having specific control
of where virtual links are placed in your OSPF configuration.
On the Ethernet Routing Switch 8800/8600, OSPF behavior follows OSPF standards; OSPF
routes cannot be learned through an ABR unless the ABR connects to the backbone or through
a virtual link.
The following figure shows how to configure a virtual link between the ABR in area 2.2.2.2 and
the ABR in area 0.0.0.0.
Configuration — OSPF and RIP
Open Shortest Path First
June 2011 49