642-902 Q&A – Implement an eBGP based solution (41-45)

Section 3 – Implement an eBGP based solution, given a network design and a set of requirements

What are the two reasons for the appearance of as the next hop for a network in the show ip bgp command output? (Choose two.) Select 2 response(s).
A. The network was originated via redistribution of an interior gateway protocol into BGP.
B. The network was defined by a static route.
C. The network was originated via a network or aggregate command.
D. The network was learned via EBGP.
E. The network was learned via IBGP.
Answer: AC

Above is the output from show ip bgp neighbors command. What is line 21 stating about the BGP connection? Select the best response.
A. the number of consecutive TCP connections to the specified remote neighbor
B. the number of times the router has established a TCP connection
C. the number of total TCP connections that the router has
D. the number of neighbors that the router has
Answer: B

The Border Gateway Protocol (BGP) is the core routing protocol of the Internet. Refer to the exhibit. Routers PGA and PGB are running BGP but the session is active. What command needs to be added to establish the BGP session?


A. ip route s0/0 ip route s0/1
B. no synchronization
C. network
D. neighbor next-hop-self
Answer: A
When BGP is running between routers in different autonomous systems, it is called External BGP (EBGP). When BGP is running between routers in the same AS, it is called Internal BGP (IBGP).
BGP allows the path that packets take to be manipulated by the AS, as described in this module. It is important to understand how BGP works to avoid creating problems for your AS as a result of running BGP. A static route can be used to form an adjacency between EBGP neighbors.

A router has two paths to reach another network in a different autonomous system. Neither route was generated by the local router and both routes have the same default weight and local preference values. Which statement is true about how BGP would select the best path? Select the best response.
A. If the command bgp always-compare-med has been given, then the router will prefer the route with the highest MED.
B. The router will prefer the route with the lower MED.
C. The router will prefer the shortest autonomous system path.
D. To influence one route to be preferred, its default local preference value will be changed via the use of the command bgp default local-preference 50.
Answer: C
The shortest AS path is the fourth item checked by BGP routers, while the MED values are one of the last items looked at by BGP routers. The following is a partial list of rules used by BGP to determine the best path. Prefer the path with the highest WEIGHT.
Note: WEIGHT is a Cisco-specific parameter, local to the router on which it’s configured. Prefer the path with the highest LOCAL_PREF. Prefer the path that was locally originated via a network or aggregate BGP subcommand, or through redistribution from an IGP. Local paths sourced by network or redistribute commands are preferred over local aggregates sourced by the aggregate address command. Prefer the path with the shortest AS_PATH. Note the following: Prefer the path with the lowest origin type: IGP is lower than EGP, and EGP is lower than INCOMPLETE. Prefer the path with the lowest multi-exit discriminator (MED).

Which one of the following statements about BGP is FALSE?
A. BGP uses TCP port 179.
B. BGP ensures reliability of updates by using the reliable transport services of TCP.
C. The network command with the mask option never installs a prefix into the BGP table unless there is a matching prefix exists in the IP route table.
D. A TCP connection is required before exchanging updates.
E. BGP uses notification and the update messages to establish and maintain the BGP neighbor relationship.
Answer: E

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