300-420 Question #164: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. An architect must design a solution to connect the two ASs. To optimize bandwidth, the design will implement load sharing between router R6 and router R4. Which solution should the design include?

Options

• AUse update-source to specify the Loopback interface.
• BUse next-hop-serf attributes only for routes that are learned from eBGP peers.
• CConfigure the eBGP TTL to support eBGP multihop.
• DUse maximum-paths to install multiple paths in the routing table.

Explanation

The architect needs to design a solution that enables load sharing between two routers connecting different ASs using eBGP to optimize bandwidth.

Common mistakes.

• A. Using update-source with a Loopback interface is a best practice for iBGP peerings to ensure BGP session stability and reachability, but it does not enable load sharing across eBGP paths.
• B. The attribute is next-hop-self, not next-hop-serf, and it is typically used for iBGP peers to ensure reachability to external networks, not for load sharing between eBGP peers.
• C. Configuring eBGP multihop by increasing the TTL (Time-to-Live) allows eBGP peers to be more than one hop away, which is useful for non-directly connected peers, but it does not enable load sharing across multiple paths.

Concept tested. BGP load sharing with maximum-paths

Reference. https://www.cisco.com/c/en/us/td/docs/ios/iproute_bgp/configuration/guide/irg_multipath_bgp.html

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