Which two statements about BGP facilitate the prevention of routing loops between two autonomous systems? (Choose two.)
Correct Answer: A,C
When an EBGP router advertises a route to a neighbor in a different AS, it appends its own AS number to the AS_PATH attribute. This helps other routers recognize the path the route has taken and prevents routing loops. If an EBGP router receives a route advertisement that already contains its own AS number in the AS_PATH attribute, it will drop the route. This prevents the router from accepting a route that would create a routing loop.
Question 52
What is the default keepalive time for BGP?
Correct Answer: B
Explanation The default keepalive time for BGP is 60 seconds1. The keepalive time is the interval at which BGP sends keepalive messages to maintain the connection with its peer1. If the keepalive message is not received within the hold time, the connection is considered lost1. By default, the hold time is three times the keepalive time, which is 180 seconds1.
Question 53
Which statement is true about IP-IP tunnels?
Correct Answer: D
Question 54
Exhibit Your BGP neighbors, one in the USA and one in France, are not establishing a connection with each other. Referring to the exhibit, which statement is correct?
Correct Answer: B
Explanation The exhibit shows the configuration of BFD liveness detection for BGP at the global level, which applies to all BGP neighbors by default1. However, this configuration does not specify the session mode, which determines whether BFD uses single-hop or multihop mode to communicate with a neighbor2. For single-hop BGP neighbors, which are directly connected on the same subnet, the session mode can be either automatic or single-hop. For multihop BGPneighbors, which are not directly connected and require multiple hops to reach, the session mode must be multihop2. Since your BGP neighbors are in different countries, they are likely to be multihop neighbors. Therefore, you need to configure the session mode as multihop for each neighbor individually at the [edit protocols bgp group group-name neighbor address bfd-liveness-detection] hierarchy level2. For example: protocols { bgp { group usa { neighbor 192.0.2.1 { bfd-liveness-detection { session-mode multihop; } } } group france { neighbor 198.51.100.1 { bfd-liveness-detection { session-mode multihop; } } } } } If you do not configure the session mode for multihop neighbors, BFD will use the default mode of automatic, which will try to use single-hop mode and fail to establish a BFD session with the remote neighbor2. This will prevent BGP from using BFD to detect liveliness and failover. Therefore, the answer B is correct, as you need to configure the BFD liveness detection on the BGP neighbor level with the appropriate session mode for multihop neighbors.
Question 55
Which command displays the output shown in the exhibit?
Correct Answer: B
This command shows the Ethernet switching table, which includes information about MAC addresses, their associated VLANs, and the interfaces they are learned on, similar to the output shown in your exhibit.
