H3C Technologies H3C SecPath F1000-E User Manual
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4.
AS external LSA
An AS external LSA originates from an ASBR, describing routing information to a destination outside the
AS.
Figure 18 AS external LSA format
Network mask
Forwarding address
LS age
Linke state ID
Advertising router
Options
5
LS sequence number
LS checksum
Length
Metric
External route tag
...
E
0
Forwarding address
TOS metric
External route tag
E
TOS
0
7
15
31
Major fields:
•
Link State ID: The IP address of another AS to be advertised. When describing a default route, the
Link State ID is always set to Default Destination (0.0.0.0) and the Network Mask is set to 0.0.0.0
•
Network mask: The IP address mask for the advertised destination
•
E (External Metric): The type of the external metric value, which is set to 1 for type 2 external routes,
and set to 0 for type 1 external routes. See
for description about external route types
•
Metric: The metric to the destination
•
Forwarding Address: Data traffic for the advertised destination will be forwarded to this address
•
External Route Tag: A tag attached to each external route. This is not used by the OSPF protocol
itself. It may be used to manage external routes.
5.
NSSA external LSA
An NSSA external LSA originates from the ASBR in a NSSA and is flooded in the NSSA area only. It has
the same format as the AS external LSA.