300-510 · Question #299
Refer to the exhibit. A Tier 1 ISP provides connectivity services to two regional ISPs, ISP1 and ISP2, leveraging the MPLS network. OSPF is used as an internal routing protocol, and BGP is used for co
The correct answer is A. Enable MPLS on all interfaces in the MPLS network within the Tier 1 ISP backbone.. The absence of a label for the VPN prefix 192.0.21.0/24 in PE2’s forwarding table indicates that MPLS wasn’t active on the path through the backbone, so PE2 is treating the route as a plain IP route. After the maintenance, one or more links likely lost their mpls ip interface con
Question
Refer to the exhibit. A Tier 1 ISP provides connectivity services to two regional ISPs, ISP1 and ISP2, leveraging the MPLS network. OSPF is used as an internal routing protocol, and BGP is used for communication with external customers. After maintenance work on the backbone, connectivity between ISP1 and ISP2 started to fail. A network engineer for the Tier 1 ISP determined that hosted shared resources with IP prefix 192.0.21.0/24 are not reachable from the IPS2 side. Which action must be taken to restore connectivity?
Exhibit
Options
- AEnable MPLS on all interfaces in the MPLS network within the Tier 1 ISP backbone.
- BIncrease the OSPF cost for routes received from ISP1 on PE1.
- CIncrease the BGP local preference for routes received from ISP1 on PE1.
- DEnable CEF on all routers in the MPLS network within the Tier 1 ISP backbone.
How the community answered
(36 responses)- A78% (28)
- B3% (1)
- C14% (5)
- D6% (2)
Explanation
The absence of a label for the VPN prefix 192.0.21.0/24 in PE2’s forwarding table indicates that MPLS wasn’t active on the path through the backbone, so PE2 is treating the route as a plain IP route. After the maintenance, one or more links likely lost their mpls ip interface configuration. Enabling MPLS on all provider-core interfaces ensures that labels are consistently pushed and popped end-to-end, restoring reachability for the VPN subnet.
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