Top 100+ Most Common BGP Interview Questions [UPDATED 2020]

Question 1 How do I configure BGP?

Question 2 Can I use BGP instead of any IGP?

Question 3  Can I run two BGP processes on single router?

Question 4  Types of BGP routing table?

Question 5 How do I configure BGP with the use of a loopback address?

Question 6  Explain Border Gateway Protocol (BGP)?

Question 7  A router is receiving same route from two different eBGP peers. The AS information contains in peer 1 is {65500, 65550, 65555} and in peer 2 is {65501, 65501}. But I want to make peer 1 preferred. How can we do that?

Question 8  What is BGP RFC 3107 or what is BGP Label Update in IPv4?

Question 9 In Multi-homing scenario if primary link gets fail, after how long traffic will be shifted to secondary link.

Question 10 BGP is link state or distance vector protocol?

Question 11 What is the order of preference of attributes when some or all are applied to one neighbor in BGP?

Question 12  What does a next hop of 0.0.0.0 mean in the show ip BGP command output?

Question 13 Can Routers on different subnet become BGP neighbors?

Question 14  What is Autonomous System?

Question 15  What is BGP Graceful Restart, NSR and NSF?

Question 16 BGP Redistribution Vs MPLS, which one you will select?

Question 17  Best practices to define BGP Communities as per RFC 1998.

Question 18  What are the well-known communities of the BGP community attribute?

Question 19  What formats can I use to configure the BGP community attribute?

Question 20 What TCP port number BGP use for connection?

Question 21 How does BGP behave differently with auto-summary enabled or disabled?

Question 22 How can I verify if a BGP router announces its BGP networks and propagates them to the global BGP mesh?

Question 23 Difference between eBGP and iBGP neighbor?

Question 24  When and how should I reset a BGP session?

Question 25  Is there any special configuration needed on PIX/ASA to allow BGP sessions through it?

Question 26 What is an autonomous system (AS) number and how do I obtain one?

Question 27 What Administrative Distance BGP uses for iBGP & eBGP ?

Question 28 What is the BGP path selection criteria?

Question 29  What is the difference between always-compare-med and deterministic-med?

Question 30  Explain Loop prevention mechanism in BGP?

Question 31  Do internal BGP (iBGP) sessions modify the next hop?

Question 32 Do external BGP (eBGP) sessions between confederations modify the next hop?

Question 33 Do we need to follow 3 way handshake process to establish BGP communication?

Question 34 In external BGP (eBGP) sessions, which IP address is sent as the next hop?

Question 35 Does route reflector come in actual path during traffic forwarding?

Question 36  Does it require that BGP router-id should reachable in cloud?

Question 37 What is recursive lookup in BGP and how it works?

Question 38 Does the route reflector change the next hop attribute of a reflected prefix?

Question 39 What is the difference between hard reset and soft reset in BGP?

Question 40  How can I announce a prefix conditionally to one ISP only when I lose the connection to my primary ISP?

Question 41 How can I configure BGP to provide load sharing and redundancy in my network?

Question 42 What are different BGP Message Types?

Question 43 What can happen if Route Reflector (RR) is not getting proper route updates?

Question 44 What is route reflector synchronization?

Question 45 How to use BGP as PE-CE backdoor link?

Question 46 How much memory should I have in my router to receive the complete BGP routing table from my ISP?

Question 47 What are the benefits of configuring BGP peer groups?

Question 48  Explain various states of BGP?

Question 49  Why do I see the same route twice from the same peer in BGP?

Question 50 What is synchronization, and how does it influence BGP routes installed in the IP routing table?

Question 51 What is the meaning of update source loopback?

Question 52 In eBGP I am establishing my neighborship with loopback address but it’s not coming up. Please specify different reasons for not coming up.

Question 53 What is Hierarchical FIB – BGP-PIC?

Question 54  If a static route is advertised in BGP without using update source what will be the next hop address in update?

Question 55 What is the advantage of using BGP AS Prepend?

Question 56 Can we use BGP as backdoor link for customers instead of OSPF? If yes, please let us know what could the issues BGP create?

Question 57  What is BGP PIC?

Question 58 What is the BGP path selection criteria?

Question 59  Define various BGP path attributes.

Question 60 Why weight doesn’t fall under path attribute category?

Question 61 What is confederation?

Question 62 Define various types of communities and why they are used?

Question 63 How do I know which Cisco IOS software release supports a particular BGP feature?

Question 64 How can I set the Multi Exit Discriminator (MED) value on prefixes advertised to external BGP (eBGP) neighbors to match the Interior Gateway Protocol (IGP) next hop metric?

Question 65 Can we redistribute BGP in IGP? Please explain your answers.

Question 66 What is cluster-id?

Question 67 I am receiving updates from eBGP peer, will the next hop change or not?

Question 68 Explain BGP Weight attribute?

Question 69 What is the difference between next-hop-self and update source loopback?

Question 70  Define loop prevention mechanism in BGP.

Question 71 What is the default BGP ConnectRetry timer, and is it possible to tune the BGP ConnectRetry timer?

Question 72 What does r RIB-Failure mean in the show ip bgp command output?

Question 73  Explain BGP Local preference?

Question 74 What is route reflector and why it is required?

Question 75 What is no-synchronization rule?

Question 76 How can I redistribute internal BGP (iBGP) learned default-route (0.0.0.0/0) route into EIGRP/OSPF/IS-IS?

Question 77 How can I filter all IP routes advertised to a BGP neighbor except the default route 0.0.0.0/0?

Question 78 How to resolve the error- “Protocol not in this image”?

Question 79  Explain BGP MED?

Question 80 What is the cost of external and internal BGP routes?

Question 81 What will happen if route reflector is not getting proper updates?

Question 82 What will happen if route reflectors does not synchronize?

Question 83 Use BGP as Link Protection in case of Dual PoP?

Question 84 BGP: timer-wheel running slow by 1 ticks appears in the debug output.

Question 85 Is it possible to track an interface and change the route availability?

Question 86 How does IP RIB Update allocate memory?

Question 87 What is Recursive Lookup?

Question 88  What is the command to see IPv6 BGP neighbors?

Question 89 Summary in BGP causes all subnets of 10.150.0.0 to be advertised?

Question 90 Why are there no statistic results when I use the debug bfd events and debug bfd packets commands?

Question 91  If BGP neighbor state is showing idle what does it mean?

Question 92 How many links can be assigned for load balancing or sharing?

Question 93  Can we use local preference outside the autonomous system?

Question 94 Does the router have to be restarted after a new BGP Neighbor Maximum Prefix is configured?

Question 95 Is there a command to check the advertised routes along with the prepend of the AS-paths?

Question 96 How does neighbor soft-reconfiguration inbound command function?

Question 97  What does the %BGP-3-NOTIFICATION: sent to neighbor *A.B.C.D passive 6/0 (cease) 0 bytes error message mean?

Question 98  What does the %IPRT-3-ROUTEINSERTERROR: Error inserting routing entry error message mean?

Question 99  Does GSR with Cisco IOS-XR support the VPLS-BGP auto-discovery feature as a Route Reflector?

Question 100 What is the command to administratively disable BGP neighborship?

Question 101 I am having two routes for remote destination but only single route is installing in routing table, what’s the reason for this?

Question 102 How to achieve Inter-AS Communication-MP-eBGP?

Question 103 How do I debug routes for a particular VRF in the Cisco IOS-XR environment?

Question 104 What is the difference between when a route is injected in BGP via redistribute command or a network command?

Question 105  How do I verify Layer 4 forwarding summary information?

Question 106 What is the difference between Local Preference and MED?

Question 107 Default BGP timers.

Question 108 When does BGP use 0.0.0.0 router id?