CCNP Route FAQ: External BGP
Q1. Enterprise Router R1, in ASN 1, connects to ISP Router I1, ASN 2, using eBGP. The single serial link between the two routers uses IP addresses 10.1.1.1 and 10.1.1.2, respectively. Both routers use their S0/0 interfaces for this link. Which of the following commands would be needed on R1 to configure eBGP? (Choose two.)
a. router bgp 2
b. router bgp 1
c. neighbor 10.1.1.2 remote-as 2
d. neighbor 10.1.1.2 Update-source 10.1.1.1
e. neighbor 10.1.1.2 Update-source S0/0
Q2. Enterprise Router R1, in ASN 1, connects to ISP Router I1, ASN 2, using eBGP. There are two parallel serial links between the two routers. The implementation plan calls for each router to base their BGP TCP connection on their respective loopback1 interfaces, with IP addresses 220.127.116.11 and 18.104.22.168, respectively. Which of the following commands would not be part of a working eBGP configuration on Router R1?
a. router bgp 1
b. neighbor 22.214.171.124 remote-as 2
c. neighbor 126.96.36.199 update-source loopback1
d. neighbor 188.8.131.52 multihop 2
Figure: Using Loopbacks with Update Source for eBGP
Q3. The following output, taken from a show ip bgp command on Router R1, lists two neighbors. In what BGP neighbor state is neighbor 184.108.40.206?
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 220.127.116.11 4 1 60 61 26 0 0 00:45:01 0 18.104.22.168 4 3 153 159 26 0 0 00:38:13 1
Q4. The following output was taken from the show ip bgp command on Router R2. In this case, which of the following commands are most likely to already be configured on R2? (Choose two.)
BGP router identifier 22.214.171.124, local AS number 11 ... Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 126.96.36.199 4 1 87 87 0 0 0 00:00:06 Idle (Admin) 188.8.131.52 4 3 173 183 41 0 0 00:58:47 2
a. router bgp 11
b. neighbor 184.108.40.206 remote-as 11
c. neighbor 220.127.116.11 prefix-limit 1
d. neighbor 18.104.22.168 shutdown
Q5. Which of the following answers is most true about the BGP Update message?
a. It lists a set of path attributes, along with a list of prefixes that use those PAs.
b. It lists a prefix/length, plus the PA settings for that prefix.
c. It lists withdrawn routes, but never in the same Update message as newly advertised routes.
d. A single Update message lists at most a single prefix/length.
Q6. The following output occurs on Router R1. Which of the following cannot be determined from this output?
R1# show ip route 22.214.171.124 255.255.255.240 Routing entry for 126.96.36.199/28 Known via “bgp 2”, distance 20, metric 0 Tag 3, type external Last update from 192.168.1.2 00:10:27 ago Routing Descriptor Blocks: * 192.168.1.2, from 192.168.1.2, 00:10:27 ago Route metric is 0, traffic share count is 1 AS Hops 2 Route tag 3
a. The type of BGP peer (iBGP or eBGP) that advertised this route to R1
b. R1’s ASN
c. The next-hop router’s ASN
d. The AS_Path length
Q7. The following line of output was extracted from the output of the show ip bgp command on Router R1. Which of the following can be determined from this output?
Network Next Hop Metric LocPrf Weight Path * 188.8.131.52/28 184.108.40.206 0 1 2 3 4 i
a. The route is learned from an eBGP peer.
b. The route has no more than three ASNs in the AS_Path.
c. The route is the best route for this prefix.
d. None of these facts can be positively determined by this output.
Q8. Router R1 has eBGP connections to I1 and I2, routers at the same ISP. The company that owns R1 can use public address range 220.127.116.11/20. The following output lists all the IP routes in R1’s routing table within this range. Which of the following answers would cause R1 to advertise the 18.104.22.168/20 prefix to its eBGP peers? (You should assume default settings for any parameters not mentioned in this question.)
R1# show ip route 22.214.171.124 255.255.240.0 longer-prefixes ! lines omitted... O 126.96.36.199/24 [110/3] via 10.5.1.1, 00:14:36, FastEthernet0/1 O 188.8.131.52/24 [110/3] via 10.5.1.1, 00:14:36, FastEthernet0/1 O 184.108.40.206/24 [110/3] via 10.5.1.1, 00:14:36, FastEthernet0/1
a. Configure R1 with the network 220.127.116.11 mask 255.255.240.0 command.
b. Configure R1 with the network 18.104.22.168 mask 255.255.240.0 summaryonly command.
c. Redistribute from OSPF into BGP, filtering so that only routes in the 22.214.171.124/20 range are redistributed.
d. Redistribute from OSPF into BGP, filtering so that only routes in the 126.96.36.199/20 range are redistributed, and create a BGP summary for 188.8.131.52/20.