350-401 Question 150
Select 3You are configuring eBGP between two directly connected routers, R1 and R2, in different autonomous systems (AS). Both routers are configured with their respective BGP AS numbers, and the neighbor command is used to establish the relationship. After applying the configuration, the BGP neighbor relationship fails to establish. Which of the following steps should you take to troubleshoot and resolve the issue?
- A
Verify that the IP address used in the
neighborcommand matches the IP address of the directly connected interface on the neighbor router. - B
Ensure that the BGP AS number configured on the neighbor matches the one specified in the
neighborcommand on the local router. - C
Check if the
update-sourcecommand is required for the neighbor relationship, and configure it if necessary. - D
Verify that the directly connected interfaces on both routers are operational and not administratively shut down.
- E
Configure the
next-hop-selfcommand to ensure proper route advertisement.
Show answer and explanation
Correct answers: A, B, D
Explanation
To establish an eBGP neighbor relationship, the local router must use the correct IP address and AS number for the neighbor. Additionally, the directly connected interfaces must be operational. Since the scenario involves directly connected neighbors, the update-source command is not relevant. Similarly, the next-hop-self command is used for route advertisement, not neighbor establishment.
- A. Correct.
The IP address in the
neighborcommand must match the IP address of the directly connected interface on the neighbor router; otherwise, the BGP session will not establish. - B. Correct.
The BGP AS number specified on the local router for the neighbor must match the neighbor's actual AS number, or the neighbor relationship will not form.
- C. Incorrect.
The
update-sourcecommand is only required if the source of the BGP session is a loopback or other interface, which is not mentioned in this scenario. - D. Correct.
If the directly connected interfaces are down or administratively shut down, the BGP session cannot establish.
- E. Incorrect.
The
next-hop-selfcommand is used for route advertisement and does not affect the establishment of the BGP neighbor relationship.