Question 15 - JN0-683 discussion

Issue Overview:

The leaf devices in an IP fabric using eBGP are advertising and receiving all routes, but the routes are not being installed in the routing table and are marked as hidden. This typically indicates an issue with the BGP configuration, particularly with next-hop handling or AS path concerns.

Corrective Actions:

B . You need to configure a next-hop self policy: This action ensures that the leaf devices modify the next-hop attribute to their own IP address before advertising routes to their peers. This is particularly important in eBGP setups where the next-hop may not be directly reachable by other peers.

D . You need to configure multipath multiple-as: This setting allows the router to accept multiple paths from different autonomous systems (ASes) and use them for load balancing. Without this, the BGP process might consider only one path and mark others as hidden.

Incorrect Statements:

A . You need to configure as-override: AS-override is used to replace the AS number in the AS-path attribute to prevent loop detection issues in MPLS VPNs, not in a typical eBGP IP fabric setup.

C . You need to configure loops 2: There is no specific BGP command loops 2 relevant to resolving hidden routes in this context. It might be confused with allowas-in, which is used to allow AS path loops under certain conditions.

Data Center

Reference:

Proper BGP configuration is crucial in IP fabrics to ensure route propagation and to prevent routes from being marked as hidden. Configuration parameters like next-hop self and multipath multiple-as are common solutions to ensure optimal route installation and load balancing in a multi-vendor environment.