Allied Telesis AT-S83 - Manual (Page 342)

Chapter 15: Open Shortest Path First (OSPF) Commands
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OSPF ABR-TYPE
Syntax
ospf abr-type cisco|ibm|shortcut|standard
no ospf abr-type cisco|ibm
Parameters
cisco Specifies an alternative OSPF Area Border
Router (ABR) type using Cisco implementation
RFC 3509. This is the default ABR type.
ibm Specifies an alternative ABR using IBM
implementation RFC 3509.
shortcut Specifies a Shortcut ABR as defined by draft-
jetf-ospf-shortcut-abr-02.txt.
standard Specifies a standard behavior ABR as defined
by RFC 2328.
Description
Use the OSPF ABR-TYPE command to set an ABR type. Specifying the
ABR type allows better functioning between different implementations.
This command is specially useful in a multi-vendor environment. The ABR
types are:
ˆ Cisco ABR Type: By this definition, a router is considered an ABR if it
has more than one area actively attached and one of them is a
backbone area.
ˆ Standard ABR Type: By this definition, a router is considered an ABR if
it has more than one area actively attached.
ˆ IBM ARB Type: By this definition, a router is considered an ABR if it
has more than one area actively attached and the backbone area is
configured. In this case, the configured backbone does not need to be
actively connected.
ˆ Shortcut ABR Type: By this definition, the Shortcut ABR is an
improvement over the standard ABR behavior by modifying the
calculation of inter-area routes. It is allowed to install inter-area routes
through non-backbone areas if the non-backbone path is better, thus
providing a shortcut through these areas. To prevent routing loops, the
inter-area routes are readvertised only if they are associated with the
backbone area.