Module Self Check
Use the questions here to review what you learned in this module. The correct answers and solutions are found in the Module Self-Check Answer Key.
Q1) Which three items are BGP enhancements to traditional distance vector routing protocols? (Choose three.) (Source: Introducing BGP)
A) reliable updates
B) use of triggered updates only
C) enhanced security
D) rich metrics
E) route summarization
F) snapshot updates
Q2) Which protocol facilitates reliable update capabilities in BGP? (Source: Introducing BGP)
A) TCP
B) UDP
C) HSRP
D) ICMP
Q3) What are three characteristics of an AS? (Choose three.) (Source: Introducing BGP)
A) uses IGPs for intradomain routing
B) uses EGPs for interdomain routing
C) is a collection of networks under a common administrative authority
D) consists of a group of network domains
E) automatically summarizes addresses
F) regulated by the IETF
Q4) Which three scenarios are common scenarios where BGP is used? (Choose three.) (Source: Introducing BGP)
A) a customer with a connection to multiple service providers
B) service provider networks acting as transit systems and forwarding external traffic through their network
C) a single-site customer intranet with complex administrative policies between departments
D) as the core routing protocol in very large enterprise networks
E) as the routing protocol in an IS-IS backbone area
F) as the core routing protocol in an SNA network
Q5) What are three recommended BGP use guidelines for multihomed customer networks? (Choose three.) (Source: Introducing BGP)
A) Most multihomed customers should use BGP with their service providers.
B) Most multihomed customers should forward routing information that is received from one provider to the other provider.
C) The multihomed customer must have its own public AS number.
D) Multihomed customers should use a provider-independent, public address space.
E) The multihomed customer may use and advertise RFC 1918 addresses.
F) Multihomed customers should use the AS number of their primary ISP.
© 2005, Cisco Systems, Inc. BGP Overview 1-117
Q6) What is a limitation of the BGP routing protocol? (Source: Introducing BGP)
A) You cannot use BGP to implement hop-by-hop routing policy controls.
B) You cannot use BGP to influence the routing policy in a downstream AS.
C) BGP cannot control forwarding of packets based on their destination address.
D) BGP cannot scale to very large networks with more than 110,000 routes.
Q7) Which three statements are true of BGP mandatory well-known attributes? (Choose three.) (Source: Understanding BGP Path Attributes)
A) They must be present in all BGP updates.
B) All BGP-compliant implementations must recognize them.
C) All BGP-compliant routers must adhere to policies specified in mandatory attributes.
D) All well-known attributes are propagated to other neighbors.
E) They must be present in some BGP updates.
Q8) Which three attributes are BGP mandatory well-known attributes? (Choose three.) (Source: Understanding BGP Path Attributes)
A) next-hop
B) weight
C) AS-path
D) origin
E) MED
F) local preference
Q9) Which three possible values are assigned to the BGP origin attribute? (Choose three.) (Source: Understanding BGP Path Attributes)
A) IGP
B) EGP
C) unknown
D) internal
E) external
F) MED
Q10) Which nontransitive optional BGP attribute is useful in assisting with the route selection process when multiple links to another AS exist? (Source: Understanding BGP Path Attributes)
A) next-hop
B) local preference
C) MED
D) AS-path
Q11) In which two ways can the BGP next-hop attribute be modified? (Choose two.) (Source: Understanding BGP Path Attributes)
A) If the next-hop attribute is in the same IP subnet as the receiving router, the attribute is unchanged; otherwise, it is set to the IP address of the sending router.
B) The next-hop attribute is always set to the IP address of the sending router.
C) The next-hop attribute is modified only when BGP packets exit an AS.
D) The BGP next-hop attribute is modified only when BGP packets traverse point-to-point links.
1-118 Configuring BGP on Cisco Routers (BGP) v3.2 © 2005, Cisco Systems, Inc.
Q12)
Q13)
Q14)
Which three statements regarding the BGP AS-path attribute are true? (Choose three.)
(Source: Understanding BGP Path Attributes)
A) The local AS number is prepended to the AS path each time that the route crosses an AS boundary.
B) The AS that originally injected the route into BGP is always found at the rightmost end of the AS path.
C) The AS-path attribute can be used to avoid routing loops.
D) BGP routes with an empty AS path were injected into BGP from outside the local AS.
E) The local AS number is appended to the end of the AS path each time that the route crosses an AS boundary.
F) The AS that originally injected the route into BGP is always found at the leftmost end of the AS path.
What is indicated by a state of "Idle" in the output of the show ip bgp summary command? (Source: Establishing BGP Sessions)
A) The router is currently not attempting to establish a connection with a neighbor.
B) The connection to the configured neighbor has timed out.
C) The connection to a BGP neighbor has been established, and no errors have been received on the connection.
D) The connection to a BGP neighbor has been established, and no packets have been sent.
What happens if two TCP connection attempts between configured BGP neighbors succeed? (Source: Establishing BGP Sessions)
A) Both connections will be terminated, and the neighbors will re-establish a neighbor relationship.
B) One connection will be maintained as primary and the other as backup.
C) One of the two connections will be torn down.
D) The router with the lower router-ID will determine if the second connection is torn down or used as a backup TCP connection.
Q15) Given the following BGP session states:
OpenConfirm
Established
Idle
OpenSent Active
What is their order of progression during the creation of a successful neighbor session? (Source: Establishing BGP Sessions)
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A) |
5, 1, |
4, |
2, |
|
B) |
3, 4, |
1, |
5, |
|
C) |
5, 4, |
1, |
3, |
|
D) |
3, 5, |
4, |
1, |
© 2005, Cisco Systems, Inc. BGP Overview 1-119
Q16) What does the field "TblVer" indicate in the output of the show ip bgp summary command? (Source: Establishing BGP Sessions)
A) the current version of BGP in use by the router
B) the number of route prefixes that are contained in the BGP update of the router
C) BGP messages that have been received from that neighbor
D) the last version of the BGP database that was sent to that neighbor
Q17) What occurs when you use MD5 between two BGP neighbors? (Source: Establishing BGP Sessions)
A) Every packet is encrypted with MD5.
B) The IP header is encrypted using MD5.
C) An MD5 checksum is calculated and sent with each packet so that its source can be verified.
D) A username and password are embedded in an IP datagram that is matched to a username and password on the remote neighbor.
Q18)
Q19)
What does a router that is running BGP do with a BGP update that contains its own AS path? (Source: Processing BGP Routes)
A) The router checks to see whether the information that is contained in the update is better than its current information. If it is, it will update its BGP table.
B) The router accepts the route update.
C) The router silently discards (denies) the route.
D) The router returns an error to the router that sent the update.
How many alternate paths to a single destination will a BGP router maintain in the BGP table? (Source: Processing BGP Routes)
A) The router will maintain only the best path to the destination.
B) The router will maintain two paths, the best path and a backup route.
C) The BGP table will hold up to four routes by default and a maximum of six configurable routes.
D) The BGP table will store all valid, advertised routes to the destination in the BGP table.
1-120 Configuring BGP on Cisco Routers (BGP) v3.2 © 2005, Cisco Systems, Inc.
Q20) When a router has more than one alternative route to reach the same IP subnet (network and mask), the router has to select one of them as best in its default mode of operation Match the following steps to the correct step in the process. (Source: Processing BGP Routes)
A) The router compares MED values, but only if it receives the updates from the same neighboring AS. Routes with a lower MED are preferred.
B) The router checks whether the next-hop attribute indicates an IP address that is reachable according to the current routing table. If the next hop is not reachable, the router does not consider the BGP route as a candidate to become selected as the best. (Source: Processing BGP Routes)
C) The router prefers the route with the higher weight.
D) If the local preference attributes are different, the route with the highest value is selected as best.
E) The lengths of the AS paths are compared (the content is not checked; only the number of autonomous systems in each AS path is counted). The route with the shortest length is selected.
F) If one of the routes is injected into the BGP table by the local router, the local router prefers it to any routes that it receives from other BGP routers.
G) If the AS-path lengths are the same, the origin code is checked. BGP prefers the path with the lowest origin type: IGP is lower than EGP, and EGP is lower than Incomplete.
Q21) What are two ways in which local networks are advertised into the BGP routing protocol process? (Choose two.) (Source: Processing BGP Routes)
A) automatically, after a BGP neighbor session is established
B) manually, with the network command
C) through redistribution into the BGP process
D) by advertising them to the BGP table on the router after Cisco Discovery Protocol discovers connected networks
Q22) What are two situations when is it appropriate to disable automatic summarization in BGP? (Choose two.) (Source: Processing BGP Routes)
A) when BGP neighbors are not configured to advertise aggregate routes to upstream providers
B) when the classless variant of the network command is used
C) when you are using a classless IGP in the AS
D) when the effects of automatic summarization of IGP-to-BGP redistribution are not desired
© 2005, Cisco Systems, Inc. BGP Overview 1-121
Q23) What is the AD of BGP routes in the IP routing table that were learned from BGP neighbors in a different AS? (Source: Processing BGP Routes)
B) 20
C) 90
D) 120
Q24) Which three BGP attributes are displayed for each route in the BGP table when you are using the show ip bgp command? (Choose three.) (Source: Processing BGP Routes)
A) weight
B) communities
C) origin
D) AS-path
Q25) What is the valid AS number range for a BGP process on a Cisco router? (Source: Configuring Basic BGP)
B) 1 to 32768
C) 1 to 65535
D) 1 to 131072
Q26) Which two parameters must you configure with the neighbor command to establish a BGP session with an external neighbor? (Choose two.) (Source: Configuring Basic BGP)
A) neighbor IP address
B) subnet mask of the IP network
C) remote AS number
D) local AS number
E) description of the neighbor
Q27) What is the best method to temporarily disable a BGP neighbor session? (Source: Configuring Basic BGP)
A) remove the neighbor command from the BGP router process
B) remove the BGP router process from the configuration
C) terminate the neighbor connection with the neighbor shutdown command
D) disconnect the neighbor by initiating a router reload
Q28) Which two of the following statements about configuring BGP timers are accurate? (Choose two.) (Source: Configuring Basic BGP)
A) Changing the BGP default holdtime and keepalive timers is usually not recommended.
B) The neighbor timers command sets the timers for a specific BGP peer or peer group.
C) The timers bgp command sets the timers for a specific BGP peer or peer group.
D) Holdtime indicates the frequency (in seconds) with which the Cisco IOS software sends messages to its peer.
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Q29) Which two of the following are characteristics of the string component of the neighbor {ip-address | peer-group-name} password string command? (Choose two.) (Source: Configuring Basic BGP)
A) can contain any alphanumeric characters, including spaces
B) case-sensitive password of up to 100 characters
C) first character can be a number
D) cannot specify a password in the format "number-space-anything"
Q30) Which three steps must you complete to advertise a classless prefix into BGP? (Choose three.) (Source: Configuring Basic BGP)
A) configure the prefix with the network command
B) specify the mask keyword with the locally advertised route
C) configure the redistribute connected command under the BGP router process
D) use a static route pointing to null 0 that matches the prefix
Q31) Which origin code is carried with routes that are redistributed into BGP? (Source: Configuring Basic BGP)
A) internal
B) external
C) unknown
D) incomplete
Q32) Which two of the following statements about the classless behavior of BGP are correct? (Choose two.) (Source: Configuring Basic BGP)
A) When an exact match is not found in the IP routing table a matching prefix is automatically configured on the router.
B) In the network ip-prefix-address mask subnet-mask command, the prefix does not have to match an entry in the IP routing table
C) To advertise classless networks into BGP (a subnet or a supernet), you can use the network command with the mask keyword and the subnet mask specified.
D) If the keyword mask and the subnet mask are omitted, the network is assumed to have its natural mask according to the network class.
Q33) What are two benefits of using route aggregation in BGP? (Choose two.) (Source: Configuring Basic BGP)
A) It ensures that even if aggregate networks are down, the aggregate is advertised, which eliminates black holes.
B) It reduces the amount of memory that is used in the router to store the BGP table.
C) It reduces route flapping and its effects on router CPU resources.
D) BGP attribute granularity is maintained, which ensures optimal path selection.
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feature? (Choose two.) (Source: Configuring Basic BGP) |
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A) |
allows you to originate a prefix into a BGP routing table without the |
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corresponding match |
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B) |
enabled with the bgp inject-map exist-map command |
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C) |
allows conditional injecting or replacing more specific prefixes with less |
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specific prefixes |
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D) |
allows origination of a prefix into a BGP routing table only with the |
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corresponding match |
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© 2005, Cisco Systems, Inc. BGP Overview 1-123
Q35) Which two of the following are characteristics of the BGP Support for TTL Security Check feature? (Choose two.) (Source: Configuring Basic BGP)
A) should be configured on only one participating router
B) prevents BGP sessions from expiring even if keepalive packets are not received before the session timer expires
C) protects the EBGP peering session by comparing the value in the TTL field of received IP packets against a hop count that is configured locally for each EBGP peering session.
D) supports both directly connected peering sessions and multihop EBGP peering sessions
Q36) Which two of the following are functions of the show ip bgp summary command? (Choose two.) (Source: Monitoring and Troubleshooting BGP)
A) displays BGP memory use
B) displays BGP neighbors and status of communication with them
C) locates problems in BGP sessions that are up and established
D) displays the BGP routing table
Q37) Which command do you use to display detailed BGP neighbor information? (Source: Monitoring and Troubleshooting BGP)
A) show ip bgp summary
Continue reading here: Transit Network Using Edge Routers as Next Hops Example
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