Pass4sure Cisco Certification

Configuring BGP on Cisco Routers Exam

Exam Number: 642-661
Associated Certifications: CCIP
Duration: 90 minutes (50-60 questions)
Available Languages: English
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Exam Description Exam Topics Recommended Training Additional Resources
Exam Description
The 642-661 BGP exam is a qualifying exam for the CCIP certification. The 642-661 BGP exam tests material covered under the Configuring BGP on Cisco Routers (BGP) v 3.1 course. The BGP exam assesses a candidate’s understanding of the theory of BGP, ability to configure BGP on Cisco IOS routers, and skills with troubleshooting on BGP. As a routing protocol, BGP is one of the underlying foundations of the Internet and new-world technologies.

Exam Topics
The following information provides general guidelines for the content likely to be included on the BGP exam. However, other related topics may also appear on any specific delivery of the exam.

BGP Overview
Introduction to BGP
Given a network scenario, identify appropriate BGP usage and its limitations

BGP Session Establishment
Given a typical BGP network scenario, describe the concept of BGP neighbors and the neighbor session establishment procedures

BGP Route Processing
Given a diagram of an operational BGP network, describe interdomain route processing, route propagation and BGP path selection

Basic BGP Configuration
Given a network consisting of multiple domains, successfully configure BGP

Monitoring and Troubleshooting BGP
Given a configured BGP network, verify proper operation and perform the steps necessary to correct basic BGP configuration errors

Route Selection Using Policy Controls
Multi-Homed BGP Networks
Given a customer scenario where connections to multiple ISPs must be supported, describe the need for influencing BGP route selection

AS-Path Filters
Given a customer scenario where connections to multiple ISPs must be supported, successfully configure BGP to influence route selection using AS path filters

Prefix-List Filters
Given a customer scenario where connections to multiple ISPs must be supported, successfully configure BGP to influence route selection using prefix-list filters

Outbound Route Filtering
Given an operational BGP network, use outbound route filtering to minimize the impact of BGP routing updates on router resources

Route-Maps as BGP Filters
Given a typical BGP network, correctly configure BGP to influence route selection using route maps

Implementing Changes in BGP Policy
Given a typical BGP network, configure the route-refresh feature to minimize the impact of expediting BGP policy updates

Route Selection Using Attributes
BGP Path Attributes
List BGP path attributes and functionality of each attribute Influencing BGP Route Selection with Weights
Given a customer scenario where multiple connections must be supported, successfully configure BGP to influence route selection using the weight attribute

BGP Local Preference
Given a customer scenario where multiple connections must be supported, successfully configure BGP to influence route selection using the local preference attribute

BGP Multi-Exit-Discriminator (MED)
Given a customer scenario where multiple connections must be supported, successfully configure BGP to influence route selection using the Multi-Exit-Discriminator (MED) attribute

BGP Communities
Given a customer scenario where multiple connections must be supported, successfully configure BGP to influence route selection using BGP community attributes

Customer-to-Provider Connectivity with BGP
Customer Connectivity Requirements
Describe the requirements to connect customer networks to the Internet in a service provider environment

Static Routing Toward the Customer
Given a service provider network, implement customer connectivity using static routing

BGP Customer Multi-Homed to a Single Service Provider
Given a customer scenario where multiple connections to a single ISP must be supported, implement customer connectivity with BGP

BGP Customer Multi-Homed to Multiple Service Providers
Given a customer scenario where connections to multiple ISPs must be supported, implement customer connectivity with BGP

BGP Transit Autonomous System
Transit Autonomous System Functions
Describe the function of a transit autonomous system and the need for IBGP IBGP and EBGP Interaction in a Transit AS
Given a transit autonomous system, describe the interaction between EBGP and IBGP in relation to relevant BGP attributes

Packet Forwarding in Transit Autonomous Systems
Describe the function of an IGP in forwarding packets through an autonomous system

Configuring a Transit Autonomous System
Given a BGP network scenario, successfully configure an autonomous system to act as a transit backbone

Monitoring and Troubleshooting IBGP in Transit AS
Given a configured BGP transit network, verify proper operation and perform the steps necessary to correct basic IBGP configuration errors

BGP Route Reflectors
Introduction to Route Reflectors
Describe the function and operation of route reflectors in a BGP environment

Network Design with Route Reflectors
Based upon established route reflector design rules, describe the concept of hierarchial route reflectors and their requirements

Configuring and Monitoring Route Reflectors
Given an existing IBGP network, configure and verify proper operation of route reflectors to modify IBGGP split-horizon rules

Advanced BGP Configuration
Limiting the Number of Prefixes Received from a BGP Neighbor
Given a typical BGP network, successfully configure BGP to limit the number of prefixes received from a neighbor

AS-Path Prepending
Given a typical service provider network with connections to multiple autonomous systems, use AS-Path prepending to influence the return path selected by the neighboring autonomous systems

BGP Peer Group
Given a typical BGP network, use BGP peer groups to share common configuration parameters between multiple BGP peers

BGP Route Flap Dampening
Given a properly configured BGP network, use route flap dampening to minimize the impact of unstable routes

Scaling IGP and BGP in Service Provider Networks
Common Routing Issues in Service Provider Networks
Describe common routing concerns of service provider networks

Optical Networking Designs
Describe the scalability issues of using OSPF and IS-IS as interior gateway protocols in a service provider network and list solutions for each

Scaling BGP in Service Provider Networks
Describe common scalability issues when using BGP in a service provider network and list solutions for each

QUESTION 1:

Exhibit:
Certkiller router#show ip route
Codes: C – connected, S – static, I – IGRP, R – RIP, M – mobile, B – BGP
D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2
E1 – OSPF external type 1, E2 – OSPF external type 2, EEGP
i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, *
-candidate default
U – per-user static route, o – ODR T – traffic engineered route Gateway of last resort is not set
172.16.0.0/24 is subnetted, 2 subnets
B 172.16.10.0 [20/0] via 10.1.1.100, 00:00:24
B 172.16.11.0 [20/0] via 10.1.1.100, 00:00:24
172.26.0.0/28 is subnetted, 3 subnets
B 172.26.1.48 [200/0] via 192.168.1.50, 00:00:31
B 172.26.1.32 [200/0] via 192.168.1.50, 00:00:31
B 172.26.1.16 [200/0] via 192.168.1.50, 00:00:31
10.0.0.0/8 is variable subnetted, 2 subnets, 2 masks
B 10.0.0/8 [20/0] via 10.1.1.100, 00:00:24
C 10.1.1.0/24 is directly connected, Serial3
192.168.1.0/28 is subnetted, 3 subnets
C 192.168.1.32 is directly connected, Serial1
C 192.168.1.48 is directly connected, Serial2
C 192.168.1.16 is directly connected, Serial0
192.168.2.0/24 is variably subnetted, 2 subnets, 2 masks
B 192.168.2.64/28 [20/0] via 10.1.1.100, 00:00:26
Based on the show ip route output in the exhibit, how can you tell if a BGP route is learned via IBGP or EBGP?

A. By the Metric
B. By the Next Hop
C. By the Admin Distance
D. By the code “B” or “B Ex” Answer: C
Explanation: admin distance. Distance of EBGP is 20, Distance of IBGP is 200.

QUESTION 2:
What is the range of values from which an ISP can assign a private AS number? A. 32768 to 65535
B. 64512 to 65535
C. 65101 to 65535
D. 65001 to 65535
Answer: B Explanation:
An autonomous system (AS) is a collection of networks under a single technical administration. Some other definitions refer to a collection of routers or IP prefixes, but
in the end they all mean the same entity. The important principle is the technical administration, which means sharing the same routing protocol and routing policy. Legal and administrative ownership of the routers does not matter in terms of autonomous systems. Autonomous systems are identified by AS numbers, 16-bit unsigned quantities ranging from 1 to 65535. Public AS numbers are assigned by Internet registries. For customers that need AS numbers to run BGP in their private networks, a range of private AS numbers (64512 – 65535) has been reserved.
Reference: Configuring BGP on Cisco Routers volume 1 p.2-4

QUESTION 3:

Network topology exhibit

What can prevent the corresponding BGP session from being successfully established?

A. Certkiller 2 and Certkiller 5 cannot establish the IBGP session because Certkiller 2 and
Certkiller 5 are not directly connected.
B. Certkiller 1 and Certkiller 2 establish the EBGP session if the BGP holddown timers between the two EBGP neighbors are different.
C. Certkiller 2 and Certkiller 5 cannot establish the IBGP session using the loopback0
interface if the EBGP-multihop value is set to the default value.
D. Certkiller 1 and Certkiller 2 cannot establish the EBGP session using the loopback0
interface if the EBGP-multihop value is set to the default value.

Answer: D

QUESTION 4:

Exhibit:

How should the EBGP session between R1 and R2 be established to enable load balancing? (Choose three)

A. Use the maximum-paths 2 option. B. Use the ebgp-multihop 2 option.
C. Use static routes on R1 and R2 to reach the other router’s loopback.
D. Establish a single EBGP session using the loopback0 interface IP address on R1 and R2.
E. Establish twp EBGP sessions using both the S0 and S1 interface IP address on R1 and R2. Answer: B, C, D
Explanation:
1. B R1 – R2 requires a EBGP ebgp-multihop of 2.
2. C Requires two static routes going to each other router loopback interface
3. D A BGP session of course is required. Only a single connection is required. Use the loopback is what allows things to work even during a failure
Wrong Answer
1. A This is not required because there is only on EBGP path. Would need two if static routes were not define and were going between different routers
2. E Not an efficient way of doing things requires double the tables and bandwidth for updates

QUESTION 5:

Which two statements are true about an EBGP session or an IBGP session? (Choose two.)

A. IBGP uses AS-Path to detect routing information loops within the AS.
B. EBGP routes have a default Admin Distance of 20 and IBGP routes have a default
Admin Distance of 200.
C. No BGP attributes are changed in EBGP updates except for the next-hop attribute if next-hop-self is configured.
D. Routes learned from an EBGP peer not advertised to another EBGP peer to prevent routing information loops.
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Recommended Training about 642-661 exam PDF
The following courses are the recommended training for 642-661 exam PDF.
642-661 Q & A with Explanations
642-661 Audio Exam
642-661 Study Guide
642-661 Preparation Lab

Exam Number/Code: 642-661
Exam Name: CCIP Configuring BGP on Cisco Routers (BGP)
VUE Code: 642-661
Questions Type: Single choice,
Question Numbers of Real-exam: 50-60 questions

“CCIP Configuring BGP on Cisco Routers (BGP)”, also known as 642-661 exam, is a Cisco certification.
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