Configuring Inbound Path Selection

A.

In a multihomed architecture, where a network is connected to multiple service providers, Border Gateway Protocol (BGP) is used to exchange routing information between the network and the providers. BGP allows the network to influence inbound traffic by advertising more preferred routes to the providers.

To influence inbound path selection, the engineer must configure a route map with AS-PATH attribute. AS-PATH is a BGP attribute that identifies the autonomous systems (AS) through which the BGP update message has passed. By manipulating the AS-PATH attribute, the engineer can control the path selection of inbound traffic.

For example, the engineer can prepend the AS-PATH with its own AS number multiple times, making the path appear longer to the provider. This will make the provider prefer a path with a shorter AS-PATH, resulting in inbound traffic being routed through the other provider.

Option B, An offset list to set the metric for routes received from neighboring autonomous systems, is not relevant for inbound path selection. Offset lists are used to adjust the metric of BGP routes advertised by a neighboring AS.

Option C, An access list to identify traffic and enable it on both of the provider-facing interfaces, is also not relevant for inbound path selection. Access lists are used to filter traffic based on source/destination IP address, protocol, port number, etc.

Option D, A route map with WEIGHT attribute to control the inbound traffic, is incorrect. WEIGHT is a Cisco-specific attribute used to influence the path selection within a single router, and it is not exchanged between BGP routers. Therefore, it cannot be used to influence inbound traffic from a provider.