Home » Juniper » JN0-661 » Which technology will allow CE1 to receive Type 1 and Type 2 LSAs from CE2?
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ISP1 has created an L3VPN to connect CE1 and CE2. The PE-CE routing protocol is OSPF.
Referring to the exhibit, which technology will allow CE1 to receive Type 1 and Type 2 LSAs from CE2?
A. OSPF sham links
B. RIB groups
C. OSPF domain IDs
D. OSPF virtual links
Correct Answer: D
Explanation/Reference:
OSPF requires that all areas in an autonomous system (AS) must be physically connected to the backbone area (area 0). In large networks with many areas, in which direct connectivity between all areas and the backbone area is physically difficult or impossible, you can configure virtual links to connect noncontiguous areas. Virtual links use a transit area that contains two or more area border routers (ABRs) to pass network traffic from one adjacent area to another.
Incorrect Answers:
A: You can create an intra-area link or sham link between two provider edge (PE) routing devices so that the VPN backbone is preferred over the backdoor link. A back-door link is a backup link that connects customer edge (CE) devices in case the VPN backbone is unavailable. When such a backup link is available and the CE devices are in the same OSPF area, the default behavior is to prefer this backup link over the VPN backbone. This is because the backup link is considered an intra-area link, while the VPN backbone is always considered an interarea link. Intra-area links are always preferred over interarea links.
B: A RIB group is a way to have a routing protocol, in most cases, place information in multiple route tables.
C: When OSPF is used as the routing protocol on a provider edge to customer edge (PE-CE) link in a multiprotocol label switching (MPLS) VPN. PE routers mark OSPF routes with the domain attribute derived from the OSPF process number to indicate whether the route originated within the same
OSPF domain or from outside it. If the OSPF process numbering is inconsistent on PE routers in the MPLS VPN, the domain-id OSPF mode command should be used to mark that the OSPF processes with different numbers belong to the same OSPF domain.
References: http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/47866-ospfdb7.html
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