Digisol DG-GS4826S, Management Manual

Page: 1235 / 1344

C
HAPTER
48 | IP Routing Commands
Open Shortest Path First (OSPFv3)
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abr-type
This command sets the criteria used to determine if this router can declare
itself an ABR and issue Type 3 and Type 4 summary LSAs. Use the no form
to restore the default setting.
S
YNTAX
abr-type { cisco | ibm | standard }
no abr-type
cisco - ABR criteria and functional behavior is based on RFC 3509.
ibm - ABR criteria and functional behavior is briefly described in
RFC 3509, and fully documented in IBM Nways Multiprotocol
Routing Services (MRS) 3.3.
standard - ABR criteria and functional behavior is based on
RFC 2328.
C
OMMAND
M
ODE
Router Configuration
D
EFAULT
S
ETTING
cisco
C
OMMAND
U
SAGE
u
The basic criteria for a router to serve as an ABR is shown below:
n
Cisco Systems Interpretation: A router is considered to be an ABR if
it has more than one area actively attached and one of them is the
backbone area.
n
IBM Interpretation: A router is considered to be an ABR if it has
more than one actively attached area and the backbone area is
configured.
n
Standard Interpretation: A router is considered to be an ABR if it is
attached to two or more areas. It does not have to be attached to
the backbone area.
u
To successfully route traffic to inter-area and AS external destinations,
an ABR must be connected to the backbone. If an ABR has no backbone
connection, all traffic destined for areas not connected to it or outside
the AS will be dropped. This situation is normally resolved, by
configuring a virtual link from the ABR to the backbone area.
u
In both the Cisco and IBM interpretation, a router connected to more
than one area cannot issue a Type 1 router LSA declaring itself as an
ABR unless it meets the other criteria listed above.
Routing table calculations are changed to allow the router to consider
summary-LSAs from all attached areas if it is not an ABR, but has more
than one attached area, or it does not have an active backbone
connection.