OSPF - LSA TYPE 7

Operation of LSA Type 7 on NSSA areas. How translation is performed by the ABR's from a LSA Type 7 to a LSA type 5 and the calculations performed with the forward address to get the metric to any specific route

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Video Description

NSSA External LSA Type 7
They describe networks that are external to the OSPF domain in areas NSSA

Generated by the ASBR in areas NSSA

Have "basically" the following information: 
External Network (link-id) / Network Mask
Router-id of the ASBR
Metric
Type of metric (Type 1 y 2)
Type 2: The nearest exit to the external network
Type 1: The exit with the lowest total metric (taking into account the internal cost)
Forward Address

Within the area where the ASBR resides, the metric is calculated:
Metric of the ASBR to the network + Metric to reach the FA of the ASBR

Outside of the area where the ASBR resides, the metric is calculated: 
Metric of the ASBR to the network  + Metric of the ABR to the FA of the ASBR + Metric to the ABR

The type 7 LSAs are translated to type 5 by the ABR with the highest router-id (in case there are multiple), when they are sent to Area 0. Keeping the original Forward Address of the type 7 LSA.

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