Implementing Cisco Enterprise Advanced Routing and Services (ENARSI) — Question 239

What is the purpose of an OSPF sham-link?

Answer options

• A. to allow inter-area routing when OSPF is used as the PE-CE connection protocol in an MPLS VPN network
• B. to allow intra-area routing when OSPF is used as the PE-CE connection protocol in an MPLS VPN network
• C. to correct OSPF backdoor routing when OSPF is used as the PE-CE connection protocol in an MPLS VPN network
• D. to correct OSPF backdoor routing when OSPF is used as the PE-PE connection protocol in an MPLS VPN network

Correct answer: C

Explanation

The correct answer is C because an OSPF sham-link is specifically designed to address backdoor routing issues in MPLS VPNs where OSPF is used as the PE-CE protocol. Options A and B incorrectly refer to inter-area and intra-area routing, which are not the purpose of a sham-link, while option D misidentifies the connection type as PE-PE instead of PE-CE.