BGP Fundamentals 2
Here you will find answers to BGP Fundamentals – Part 2
Question 1
In a multihomed environment with two ISP connections, which two statements are true? (Choose two)
A. The customer should not be configured to act as a transit AS between the two ISPs.
B. It is recommended that the multi-homed customer use a registered (public) AS number.
C. AS-Path prepending can be configured on the customer’s edge router
to influence the BGP path selection process for the outbound traffic
(traffic from the customer to the ISPs).
D. The customer can use Local Preference on the customer’s edge routers
to influence the BGP path selection process for the inbound traffic
(traffic from the ISPs to the customer).
E. The advertisement of the customer’s IP address space can be
conditioned by the customer’s edge routers by using a static route to
the nullO interface and by using the proper network statement under
router bgp
Answer: A B
Question 2
Which four attributes are used by BGP to detect routing loops? (Choose four)
A. AS-Path
B. Cluster ID
C. Cluster List
D. Originator ID
E. Community ID
Answer: A B C D
Question 3
Which three statements are true about route reflectors? (Choose three)
A. If the route is learned from an EBGP peer by the route reflector, it is reflected to all IBGP and EBGP peers.
B. If the route is learned from a non-client IBGP peer by the route reflector, it is reflected to all EBGP peers only.
C. If the route is learned from a non-client IBGP peer by the route reflector, it is reflected to EBGP peers and clients only.
D. If the route is learned from a client IBGP peer by the route
reflector, it is reflected to all clients only, except the originating
client.
E. If the route is learned from a client IBGP peer by the route
reflector, it is reflected to all EBGP peers, non-clients, and clients
(except the originating client).
Answer: A C E
Question 4
Based on the following show ip bgp neighbors 2.2.2.2 output, which two statements are true? (Choose two)
R1#show ip bgp neighbors 2.2.2.2
BGP neighbor is 2.2.2.2, remote AS 102, internal link
Index 1, Offset 0, Mask 0x2
BGP version 4, remote router ID 66.0.0.1
BGP state=Established, table version=1, up for 00:14:52
Last read 00:00:52, hold time is 180, keepalive interval is 60 seconds
Minimum time between advertisement runs is 5 seconds
Received 233 messages, 0 notifications, 0 in queue
Sent 206 messages, 0 notifications, 0 in queue
Prefix advertised 0, suppressed 0, withdrawn 0
Connections established 17; dropped 16
Last reset 00:15:02, due to User reset
18 accepted prefixes consume 576 bytes, maximum limit 20
Threshold for warning message 80%
0 history paths consume 0 bytes
A. R1 has accepted 20 prefixes from the 2.2.2.2 IBGP neighbor.
B. R1 generated a warning message to the router’s console after the 2.2.2.2 IBGP neighbor sent 16 prefixes to R1.
C. R1 generated a warning message to the router’s console after the 2.2.2.2 IBGP neighbor sent 15 prefixes to R1.
D. R1 will drop its neighbor relationship to the 2.2.2.2 IBGP neighbor if 2.2.2.2 sends two more additional prefixes to R1.
E. R1 will drop its neighbor relationship to the 2.2.2.2 IBGP neighbor if 2.2.2.2 sends three more additional prefixes to R1.
Answer: B E
Question 5
During the autonomous system number migration process, which BGP
feature allows a BGP router to act as a router within one autonomous
system to some BGP neighbors but also appear to be in another autonomous
system to other neighbors?
A. remove-private-as
B. local-as
C. as-path prepending
D. AS override
E. Site-of-Origin (Soo)
Answer: B
Question 6
Based on this configuration, which two peering router neighbor statements are correct? (Choose two)
router bgp 50001
neighbor 192.168.1.1 remote-as 50001
neighbor 10.1.1.1 remote-as 50002
neighbor 10.1.1.1 local-as 50003
!
output omitted
A. EBGP – neighbor 10.1.1.2 remote-as 50003
B. EBGP – neighbor 10.1.1.2 remote-as 50001
C. EBGP – neighbor 10.1.1.2 remote-as 50001 and neighbor 10.1.1.2 local-as 50003
D. IBGP – neighbor 192.168.1.2 remote-as 50001
E. IBGP – neighbor 192.168.1.2 remote-as 50003
F. IBGP – neighbor 192.168.1.2 remote-as 50003 and neighbor 192.168.1.2 local-as 50001
Answer: A D
Question 7
Which command is used to advertise a summary route while suppressing only a subset of the more specific routes?
A. network {ip prefix} {mask}
B. network {ip prefix} {mask} unsuppress-map {route-map-name}
C. aggregate-address {ip prefix} {mask}
D. aggregate-address {ip prefix} {mask} summary-only
E. aggregate-address {ip prefix} {mask} suppress-map {route-map-name}
F. aggregate-address {ip prefix} {mask} as-set summary-only
Answer: E
Question 8
What is the correct command to set the BGP scanner interval to two minutes?
A. bgp scan-time 2
B. bgp scan-time 120
C. bgp scan-time 2 60
D. The maximum scanning interval cannot exceed one minute
Answer: D
Question 9
Given the AS-path of
(51002 51003) 51001 i from the
show ip bgp output, what is the origin?
A. AS 51001
B. AS 51002
C. AS 51003
D. (51002 51003)
E. IGP
F. IBGP
Answer: E
Question 10
AS-PATH prepending is used in AS1 in order to influence the return
traffic path from AS 5 to AS 1 through the higher speed path via AS 2.
______ needs to be configured for AS-Path prepending and a minimum of
______ of the AS number should be prepended.
A. R1; one copy
B. R2; one copy
C. R1; two copies
D. R2; two copied
E. R2; three copies
Answer: C
Question 11
Which two configuration commands will complete the BGP configuration
on R1 so it will conditionally announce the 172.0.0.0/8 prefix to R4 via
BGP? (Choose two)
hostname R1
!
output omitted
!
1. ______________________
!
router bgp 65001
neighbor 172.16.1.1 remote-as 65001
neighbor 2.2.2.2 remote-as 65001
neighbor 4.4.4.4 remote-as 387
!
2. ______________________
A. 2. network 172.16.0.0
auto-summary
B. 2. network 172.0.0.0 mask 255.0.0.0
C. 1. ip route 172.0.0.0 255.0.0.0 null0
D. 1. ip route 172.0.0.0 255.0.0.0 null0 255
E. 1. ip route 172.0.0.0 255.0.0.0 172.16.1.1
F. 2. aggregate-address 172.0.0.0 mask 255.0.0.0
Answer: B E
Question 12
R2 is configured to prepend AS number 65102 in updates to R3. Which statement is true?
A. The BGP updates from R2 to R3 will be rejected by R3 due to loop prevention.
B. The EBGP session between R2 and R3 will be dropped due to an AS-Path prepend configuration error.
C. The AS-Path length via AS 65102 will increase to influence the return traffic path selected by the remote ASs.
D. The AS-Path length via AS 65102 will decrease to influence the return traffic path selected by the remote ASs.
E. The AS-Path prepend configuration command using the remote AS number (65102) will be rejected by IOS at R2.
Answer: A
Question 13
Refer to the partial topology diagram shown.
Service Provider 1 (SP1) assigned the customer an AS number of 65275.
Service Provider 2 (SP2) assigned an AS number of 65745 to the customer.
The customer decides to use AS 65275 internally.
Which of the following is the correct partial router configuration to
cause updates from CR1 to SP1 to report a source AS of 65275, while
updates from CR2 to SP2 report the source AS of 65745 in addition to AS
65275?
A.
!
CR1
router bgp 65275
neighbor 1.1.1.1 remote-as 65274
neighbor 10.1.1.2 remote-as 65275
CR2
router bgp 65275
neighbor 2.2.2.2 remote-as 65732
neighbor 2.2.2.2 local-as 65745
neighbor 10.1.1.1 remote-as 65275
B.
!
CR1
router bgp 65275
neighbor 1.1.1.1 remote-as 65274
neighbor 10.1.1.2 remote-as 65275
CR2
router bgp 65745
neighbor 2.2.2.2 remote-as 65732
neighbor 2.2.2.2 local-as 65745
neighbor 10.1.1.1 remote-as 65275
C.
!
CR1
router bgp 65275
neighbor 1.1.1.1 remote-as 65274
neighbor 1.1.1.1 local-as 65745
neighbor 10.1.1.2 remote-as 65275
CR2
router bgp 65275
neighbor 2.2.2.2 remote-as 65732
neighbor 2.2.2.2 local-as 65745
neighbor 10.1.1.1 remote-as 65275
D.
!
CR1
router bgp 65275
neighbor 1.1.1.1 remote-as 65274
neighbor 10.1.1.2 remote-as 65275
CR2
router bgp 65745
neighbor 2.2.2.2 remote-as 65732
neighbor 2.2.2.2 local-as 65275
neighbor 10.1.1.1 remote-as 65275
Answer: A
Question 14
In the diagram, the customer is using static routing to connect to
the ISP. Which configuration on the ISP edge routers will enable load
balancing and backup of the traffic to the customer?
A.
R1
ip route 10.1.1.0 255.255.255.128 serial 0
R2
ip route 10.1.1.128 255.255.255.128 serial 0
B.
R1
ip route 10.1.1.0 255.255.255.0 serial 0
R2
ip route 10.1.1.128 255.255.255.0 serial0
C.
R1
ip route 10.1.1.0 255.255.255.128 serial 0
ip route 10.1.1.128 255.255.255.128 serial 0
R2
ip route 10.1.1.128 255.255.255.128 serial 0
ip route 10.1.1.0 255.255.255.128 serial 0
D.
R1
ip route 10.1.1.0 255.255.255.128 serial 0
ip route 10.1.1.0 255.255.255.0 serial 0
R2
ip route 10.1.1.128 255.255.255.128 serial 0
ip route 10.1.1.0 255.255.255.0 serial 0
Answer: D
Question 15
An OSPF LSA type 1 route is redistributed into MP-BGP. That same
route is then redistributed back from MP-BGP into OSPF on another PE
router. In this case, which LSA type on the destination CE router will
the OSPF route appear as?
A. LSA type 1
B. LSA type 2
C. LSA type 3
D. LSA type 4
E. LSA type 5
F. LSA type 7
Answer: C
Question 16
When using the redistribute ospf {process-id} command, which types of OSPF routes will be redistributed into BGP?
A. all internal (interarea and intra-area) OSPF routes
B. all external OSPF routes
C. all external OSPF routes except type 7 LSAs
D. both internal and external OSPF routes
E. only classful OSPF routes without the subnet option
F. only external OSPF routes without the match option
Answer: A
Question 17
What best describes the following configuration example of allowas-in?
router bgp 100
address-family ipv4 vrf CustomerA
neighbor 195.12.4.5 remote-as 123
neighbor 195.12.4.5 activate
neighbor 195.12.4.5 allowas-in 2
A. permits incoming BGP updates defined by access-list 2
B. permits incoming BGP updates defined by class-map 2
C. permit incoming BGP updates defined by route-map 2
D. permits incoming BGP updates with no more than two occurrences of AS 100 in the AS path
E. permits incoming BGP updates with no more than two occurrences of AS 123 in the AS path
Answer: D
Question 18
Who should use private AS numbers?
A. multihomed customers who configured their AS as a transit AS
B. customers multihomed to two different ISPs
C. customers multihomed to a single ISP using multiple permanent links
D. customers connected to a single ISP using a single permanent link
Answer: C
Question 19
Refer to the outputs shown in the exhibit. What could be preventing
the R1 router from receiving any prefixes from the R2 BGP neighbor?
R1#show ip bgp summary
BSP router identifier 199.199.199.199, local AS number 20
BGP table version is 45, main routing table version 45
44 network entries using 4444 bytes of memory
81 path entries using 3888 bytes of memory
13 BGP path attribute entries using 780 bytes of memory
11 BGP AS-PATH entries using 264 bytes of memory
4 BGP route-map cache entries using 64 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 9440 total bytes of memory
BGP activity 88/44 prefixes, 191/110 paths, scan interval 5 secs
| Neighbor |
V |
AS |
MsgRcvd |
MsgSent |
TblVer |
InQ |
OutQ |
Up/Down |
State/PfxRcd |
| 192.168.1.17 |
4 |
1 |
1628 |
2693 |
45 |
0 |
0 |
00:42:22 |
31 |
| 192.168.20.22 |
4 |
22 |
70 |
73 |
45 |
0 |
0 |
00:42:26 |
31 |
| 192.168.31.1 |
4 |
65002 |
172 |
274 |
0 |
0 |
0 |
00:00:13 |
Idle |
R1#telnet 192.168.31.1
Trying 192.168.31.1 … Open
User Access Verification
Password: cisco
R2#sh run | begin bgp
router bgp 65002
bgp confederation identifier 1
bgp confederation peers 65001
network 10.0.0.0
neighbor 192.168.31.2 remote-as 20
A. There is a TCP session establishment problem between R1 and R2.
B. The no sync command is missing on R2.
C. The no sync command is missing on R1.
D. R2 is using the wrong AS number in its neighbor 192.168.31.2 remote-as statement.
E. R1 is using the wrong AS number in its neighbor 192.168.31.1 remote-as statement.
F. Both R1 and R2 are not using a loopback address to source their BGP packets.
Answer: E