642-661 - BGP - Configuring BGP on Cisco Routers Exam
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Which BGP path attribute is only used within the local router and NOT shared between all the BGP routers within the AS?
Which two statements are true about multihomed customers? (Choose two)
The customer usually uses provider independent (PI) address space.
The customer runs BGP with the service provider using either a private or a public AS number.
Which prefix-list will permit the 172.16.1.32 255.255.255.240 prefix?
ip prefix-list test permit 172.16.1.0/8 le 30
Which condition must be met before Route Refresh messages can be sent to a BGP peer?
The BGP peer must advertise Route Refresh capability.
Besides BGP policy scaling and IBGP mesh scaling, service providers need to concentrate on controlling _______.
The number of BGP updates and the size of the BGP forwarding tables using route aggregation.
What is the range of values from which an ISP can assign a private AS number?
64512 to 65535
Complete the BGP configuration on 1 so that the show ip bgp output reflects the following path selection? 1#show ip bgp BGP table version is 9, local router ID is 172.16.10.1 Status codes: s suppressed, d damped, h history, *valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric LocPrf Weight Path *> 172.20.0.0 10.10.20.1 150 65123 65122 i * 10.10.10.2 0 120 65122 i *> 172.25.0.0 10.10.21.1 150 65123 65124 i * 10.10.10.2 120 65122 65124 i *> 172.30.0.0 10.10.21.1 0 150 65123 i * 10.10.10.2 120 65122 65123 I hostname 1 ! router bgp 65121 neighbor 10.10.10.2 remote-as 65122 neighbor 10.10.20.1 remote-as 65123 ________________________
neighbor 10.10.10.2 weight 120 neighbor 10.10.20.1 weight 150
Which prefix-list statement can be used to deny all Class C Private IP addresses?
ip prefix-list blkc seq 5 deny 192.168.0.0/16 le 32
By default, which BGP path attribute is stripped in the outgoing IBGP updates?
What type of BGP path attributes are propagated to BGP peers with the partial bit set even if they are not recognized?
The purpose of the bgp always-compare-med command is to compare the MED ______.
Even if the routes originate in different ASs.
AS 65101 is a dual home customer. When starting the EBGP sessions with both ISPs announcing its networks, which two statements are true about the default behavior of BGP? (Choose two)
The default BGP route selection prefers the shortest AS-Path.
The bandwidth available to reach the ISPs is not taken into consideration in the BGP path selection process.
What does the route map named test in the following BGP configuration accomplish? router bgp 65111 neighbor 10.1.1.1 remote-as 65112 neighbor 10.1.1.1 route-map test out ! ip as-path access-list 1 permit_65222$ ip as-path access-list 2 permit.* ! route-map test permit 10 match as-path 1 set metric 200 ! route-map test permit 20 match as-path 2
Marks all prefixes originating in autonomous system 65222 advertised to the 10.1.1.1 neighbor with a MED of 200.
Which optional configuration parameter is required on a static route so a route-map can be used to match the static route?
In a multihomed environment with two ISP connections, which two statements are true? (Choose two)
The customer should not be configured to act as a transit AS between the two ISPs.
The advertisement of customer's IP address space can be conditioned by the customer's edge routers by using a static route to the null0 interface and by using the proper network statement under router bgp.
Based on the following show ip bgp neighbor 10.1.1.1 output: R1#show ip bgp neighbors 10.1.1.1 BGP neighbor is 10.1.1.1, remote AS 65103, external link BGP version 4, remote under ID 0.0.0.0 BGP state = Active Last read 00:00:04, hold time is 180, keepalive interval is 60 seconds Received 44 messages, 0 notifications, 0 in queue Sent 45 messages, 6 notifications, 0 in queue Route refresh request: received 0, sent 0 Default minimum time between advertisement runs in 30 seconds For address family: IPv4 Unicast BGP table version 1, neighbor version 0 Index 2, Offset 0, Mask 0x4 0 accepted prefixes consume 0 bytes Prefix advertised 0, suppressed 0, withdraw 0 Number of NLRIs in the update sent: max 0, min 0 Connections established 7; dropped 7 Last reset 00:05:18, due to BGP Notification received, peer in wrong AS External BGP neighbor may be up to 2 hops away. No active TCP connection What is causing the BGP session to the 10.1.1.1 neighbor to toggle between the Idle and Active state?
There is an AS number configuration error.
Which Cisco IOS command is used to view the amount of CPU resources consumed (utilization) due to running BGP processes?
show process cpu | include BGP
Which regular expression can be used to match all routes originating in the local AS?
Which four attributes are used by BGP to detect routing loops? (Choose four.)
Based on the following show ip bgp neighbor 10.1.1.1 output, what is the neighbor relationship? CK1 #show ip bgp neighbor 10.1.1.1 BGP neighbor is 10.1.1.1, remote AS 65002, external link Index 2, Offset 0, Mask 0x4 BGP version 4, remote router ID 22.214.171.124 Neighbor under common administration BGP state = Established, table version = 5, up for 00:09:15 Last read 00:00:16, hold time is 180, keepalive interval is 60 seconds Minimum time between advertisement runs is 30 seconds Received 13 messages, 0 notifications, 0 in queue Sent 13 messages, 0 notifications, 0 in queue Prefix advertised 1, suppressed 0, withdrawn 0 Connections established 1; dropped 0 Last reset never 1 accepted prefixes consume 32 bytes 0 history paths consume 0 bytes External BGP neighbor may be up to 255 hops away
Neighbor 10.1.1.1 is an Intra-Confederation EBGP neighbor.
What are two methods used to configure the local-preference BGP path attribute on Cisco routers? (Choose two)
Using a route-map with the set local-preference value command.
Using the bgp default local-preference value BGP configuration command.
BGP table Address Prefix AS-Path Next hop Communities Other attr. 10.0.0.0 /8 65100 65101 126.96.36.199 65101:111 ... ... ... ... ... ... IP routing table Protocol Address Prefix Next-hop Outgoing interface BGP 10.0.0.0 /8 188.8.131.52 OSPF 184.108.40.206 /32 172.16.1.2 Ethernet 0 conn. 172.16.1.0 /24 Ethernet 0 IP routing table Protocol Address Prefix Next-hop Outgoing interface BGP 10.0.0.0 /8 220.127.116.11 OSPF 18.104.22.168 /32 172.16.1.2 Ethernet 0 conn. 172.16.1.0 /24 Ethernet 0 To forward a packet to 10.0.0.0/8, the router perform the following steps: Step 1. Search the ip routing table for a route to reach the 10.0.0.0/8 network. Step 2. ___________________________ Step 3. Find the connected outgoing interface to reach 172.16.1.2. Step 4. Arp for the 172.16.1.2 MAC address if it is not already in the ARP cache. Step 5. Store the 172.16.1.2 MAC address in the Fast Switching cache for successive packets to network 10.0.0.0. What is step 2?
Search the IP routing table for an IGP route to reach the BGP next-hop of 22.214.171.124.
Based on the following show ip bgp neighbors output from 2, which two statements are true? (Choose two) 2#show ip bgp neighbors BGP neighbor is 10.1.1.5, remote AS 65101, internal link Index 1, Offset 0, Mask 0x2 Route-Reflector Client BGP version 4, remote router ID 126.96.36.199 BGP state = Established, table version = 4, up for 00:01:29 Last read 00:00:29, hold time is 180, keepalive interval is 60 seconds Minimum time between advertisement runs is 5 seconds Received 13556 messages, 0 notifications, 0 in queue Sent 13454 messages, 0 notifications, 0 in queue Prefix advertised 0, suppressed 0, withdraw 0 Default weight 900 Inbound path policy configured Route map for incoming advertisement is test Connections established 31; dropped 30 Last reset 00:01:40, due to User reset 3 accepted prefixes consume 96 bytes 0 history paths consume 0 bytes 0 history paths consume 0 bytes
2 is a route reflector and the 10.1.1.5 neighbor is a client of 2.
2 has successfully established the IBGP session with the 10.1.1.5 neighbor.
What is the correct BGP configuration to have AS 65111 prefer the path to AS 65221 over the path to AS 65237 except for the traffic which originates in AS 65237?
router bgp 65111 neighbor 10.10.10.10 remote-as 65221 neighbor 10.20.20.20 remote-as 65237 neighbor 10.10.10.10 weight 160 neighbor 10.20.20.20 weight 150 neighbor 10.20.20.20 filter-list 1 weight 170 ! ip as-path access-list 1 permit _65237$
The Outbound Route Filter (ORF) capability is negotiated between BGP neighbors during the BGP ____ process via the _____ message.
session establishment; Open
Which two statements are true about an EBGP session or an IBGP session? (Choose two.)
EBGP routes have a default Admin Distance of 20 and IBGP routes have a default Admin Distance of 200.
IBGP uses split horizon to prevent routing information loops; routes learned from an IBGP peer are not advertised to another IBGP peer.
Given the following: router bgp 65102 neighbor 10.1.1.1 remote-as 65103 neighbor 10.2.2.2 remote-as 65104 neighbor 172.16.1.4 remote-as 65102 neighbor 10.1.1.1 route-map setlp in ! route-map setlp permit 10 match community 1 set local-preference 150 ! route-map setlp permit 20 ! ip community-list 1 permit 65103:150 What will the configuration on R1 accomplish?
Routes from AS 65103 marked with a Community of 65103: 150 will have a Local Preference of 150; all other routes will have the default Local Preference.
What are two drawbacks when the Internet is accessed through a dedicated subinterface implementation? (Select two.)
The PE routers must perform Internet routing
A separate physical link or specific WAN encapsulation is required.
Which two statements are true regarding the BGP network configuration command? (Choose two)
When using the "network ip-prefix mask subnet-mask" BGP configuration command to advertise a classless prefix into BGP, the prefix must have an exact match in the IP routing table.
When using the "network ip-prefix" BGP configuration command to advertise a major network into BGP, at least one of the subnets of the major-network must be present in the IP routing table.