QTECH
Software Configuration Manual
8-108
·
Network Mask : The network mask for the type 3 LSA; set to 0.0.0.0 for the Type-4 LSA
·
metric : The metric to the destination
&
Note : A Type-3 LSA can be used to advertise a default route, having the Link State
ID and Network Mask set to 0.0.0.0.
4)
AS external LSA
An AS external LSA originates from an ASBR, describing routing information to a destination outside the AS.
AS external LSA format
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. Refer to Route types 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.
