350-401 Question 149
Select 2An enterprise network engineer configures eBGP between two directly connected routers, R1 (AS 100) and R2 (AS 200). The following configuration is applied on R1:
router bgp 100 neighbor 192.168.1.2 remote-as 200 network 10.1.1.0 mask 255.255.255.0 !
Despite the configuration, R1 is unable to establish a BGP session with R2. Which of the following actions would resolve this issue?
- A
Ensure that 'ip bgp neighbor 192.168.1.2 update-source' is configured on R1.
- B
Verify that the IP address 192.168.1.2 is reachable from R1.
- C
Configure the 'neighbor 192.168.1.2 ebgp-multihop' command on R1.
- D
Add the 'neighbor 192.168.1.2 next-hop-self' command on R1.
- E
Verify that AS number 200 is correctly configured on R2.
Show answer and explanation
Correct answers: B, E
Explanation
To establish eBGP between directly connected neighbors, the IP address of the neighbor must be reachable, and the remote AS number on both routers must match. Option 2 ensures connectivity between neighbors, and Option 5 ensures the AS number is correctly configured on R2.
- A. Incorrect.
This is incorrect because the 'update-source' command is used to configure a specific source IP for BGP, typically in cases of loopback peering. It's not required for directly connected neighbors.
- B. Correct.
This is correct because for a BGP session to establish, the neighbor's IP address must be reachable. This is a fundamental requirement.
- C. Incorrect.
This is incorrect because 'ebgp-multihop' is used to establish BGP sessions over multiple hops. For directly connected neighbors, this is unnecessary.
- D. Incorrect.
This is incorrect because 'next-hop-self' is used to manipulate the next-hop attribute in BGP advertisements. It does not affect the establishment of the BGP neighbor relationship.
- E. Correct.
This is correct because if the AS number on R2 is misconfigured (e.g., not set to 200), the BGP session cannot be established.