Exam JN0-649 topic 1 question 4 discussion

Area-1 has no external connections. However, Area-1 has static route (172.16.31.0/24) that are not internal OSPF route. You can limit the external route advertisements to the area and advertise the static routes by designating the area an NSSA. In an NSSA, the ASBR (vMX1) generates NSSA external (Type 7) LSAs and floods them into the NSSA, where they are contained. Type-7 LSAs allow an NSSA to support the presence of ASBR and their corresponding external routing information. The ABR (vMX2) converts Type-7 LSAs into Type-5 External LSAs and leaks them to the other areas, but external routes from other areas are not advertised within the NSSA. An admin should check this and change it https://www.packetswitch.co.uk/configuring-junos-ospf-stub-and-nssa-areas/ https://www.juniper.net/documentation/us/en/software/junos/ospf/topics/ref/statement/nssa-edit-protocols-ospf.html

Should it be type 5 instead?

Type 5

Correct Answer: B. Type 4 : Passed JN0-649 with flying colors! Next goal: Pursuing JNCIS-SP to deepen my networking knowledge.

OSPF AS SCOPE link state database Type ID Adv Rtr Seq Age Opt Cksum Len Extern 10.10.10.10 10.10.10.2 0x80000001 1591 0x22 0xcb7c 36 Extern 10.10.10.11 10.10.10.2 0x80000001 1591 0x22 0xb790 36 Extern 192.168.1.0 10.10.10.2 0x80000001 1591 0x22 0xd234 36

Extern 192.168.1.0 10.10.10.2 0x80000001 1224 0x22 0xd234 36 mask 255.255.255.0 Topology default (ID 0) Type: 2, Metric: 2, Fwd addr: 10.10.10.1, Tag: 0.0.0.0 Aging timer 00:39:35 Installed 00:20:22 ago, expires in 00:39:36, sent 00:20:22 ago Last changed 00:20:22 ago, Change count: 1

ASBR Summary LSA (Type 4) is generated by ABR (Area Border Router) to inform its areas about how to reach the ASBR (Autonomous System Border Router). ASBR Summary LSA (Type 4) includes ASBR’s Router ID.

Each of the NSSA external LSAs advertised by the ASBR router is translated by the ABR into an AS external LSA. These Type 5 LSAs are then advertised to the rest of the network using a domain-flooding scope. These “new” Type 5 LSAs, in addition to the appropriate ASBR summary LSA, are seen on the router in area 2