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Nokia BGP Fundamentals for Services study materials
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Nokia BGP Fundamentals for Services practice questions

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Question 1BGP Fundamentals and Protocol Operation

In BGP, which transport protocol and port number are used to establish a peering session between two routers?

  1. TCP port 179 Correct answer.
  2. TCP port 89
  3. UDP port 179
  4. IP protocol 47

Explanation

BGP is a path-vector routing protocol that runs over a reliable transport, specifically TCP, and IANA assigns port 179 for BGP sessions. The reliable byte stream lets BGP rely on TCP for retransmission and ordering of UPDATE, OPEN, and KEEPALIVE messages.

Question 2BGP Fundamentals and Protocol Operation

A BGP speaker receives an UPDATE containing the path attributes AS_PATH and NEXT_HOP for a prefix. Which category do these attributes belong to?

  1. Well-known discretionary
  2. Optional transitive
  3. Optional non-transitive
  4. Well-known mandatory Correct answer.

Explanation

AS_PATH and NEXT_HOP are both well-known mandatory attributes, meaning every BGP speaker must recognize them and they must appear in every UPDATE that advertises a route. Their presence allows loop detection and next-hop resolution on the receiving router.

Question 3BGP Fundamentals and Protocol Operation

What is the primary purpose of the BGP KEEPALIVE message?

  1. To request retransmission of a lost UPDATE
  2. To confirm that the peer is still reachable and the session remains up Correct answer.
  3. To negotiate capabilities during session establishment
  4. To advertise newly learned network prefixes to the peer

Explanation

Once a session reaches Established, peers exchange KEEPALIVE messages at an interval derived from the configured hold timer to prove liveness. If no KEEPALIVE or UPDATE is received before the hold timer expires, the session is torn down.

Question 4BGP Fundamentals and Protocol Operation

Which BGP state indicates that the TCP connection has completed and an OPEN message has been sent, but no KEEPALIVE has yet been received?

  1. Connect
  2. Active
  3. OpenSent Correct answer.
  4. OpenConfirm

Explanation

In OpenSent the router has sent its OPEN and is waiting for the peer's OPEN. After receiving a valid OPEN it moves to OpenConfirm, where it waits for a KEEPALIVE to reach Established.

Question 5BGP Fundamentals and Protocol Operation

By default, which value does a router use as the NEXT_HOP attribute when advertising a prefix learned from an eBGP peer to an iBGP peer?

  1. 0.0.0.0
  2. The iBGP peer's interface address
  3. The advertising router's own loopback address
  4. The eBGP peer's IP address on the inter-AS link Correct answer.

Explanation

When a route is learned via eBGP and re-advertised into iBGP, the NEXT_HOP is not changed by default, so it remains the eBGP neighbor address. This is why iBGP speakers often need next-hop-self or an IGP route to that external address.

Question 6BGP Fundamentals and Protocol Operation

A router receives the same prefix from two eBGP peers with equal weight, equal LOCAL_PREF, and equal AS_PATH length. Which attribute does the standard BGP best-path algorithm evaluate next?

  1. eBGP over iBGP preference
  2. Origin Correct answer.
  3. Router ID
  4. MED

Explanation

The canonical decision order after LOCAL_PREF and AS_PATH length is ORIGIN, then MED, then eBGP over iBGP, then lowest IGP metric, and finally tie-breakers such as router ID. ORIGIN therefore precedes MED in the comparison.

Question 7BGP Fundamentals and Protocol Operation

What does the AS_PATH attribute primarily accomplish for a BGP speaker?

  1. It records the sequence of autonomous systems a route has traversed, enabling loop detection Correct answer.
  2. It identifies the exit point preferred for outbound traffic
  3. It carries the IGP metric of the originating router
  4. It indicates whether the route is internal or external to the local AS

Explanation

Each AS prepends its own AS number when advertising to an eBGP peer, so the AS_PATH lists the autonomous systems the route crossed. A router that sees its own AS number in the path discards the route, preventing routing loops.

Question 8BGP Fundamentals and Protocol Operation

Which BGP mechanism is required to advertise routes learned from one iBGP peer to another iBGP peer within the same autonomous system?

  1. A default static route
  2. An OSPF virtual link
  3. An additional eBGP peering
  4. A route reflector Correct answer.

Explanation

The iBGP split-horizon rule normally prevents a router from re-advertising iBGP-learned routes to other iBGP peers. Route reflection permits this for eligible peers under the reflector's client rules. A full iBGP mesh provides direct distribution without permitting such re-advertisement.

Question 9BGP Fundamentals and Protocol Operation

A BGP router receives an UPDATE whose AS_PATH already contains its own AS number. What does the router do with that route?

  1. Rewrites the AS_PATH and accepts it
  2. Forwards it unchanged to all peers
  3. Discards it as a loop Correct answer.
  4. Installs it with lower preference

Explanation

The AS_PATH loop-detection rule causes a speaker to reject any route whose path already lists its own AS number. This is the fundamental protection against routing loops between autonomous systems.

Question 10BGP Fundamentals and Protocol Operation

What is the effect of the LOCAL_PREF attribute in BGP path selection?

  1. It sets the IGP metric used to reach the next hop
  2. It limits the number of AS hops a route may traverse
  3. It influences outbound path choice and is only propagated within the local AS Correct answer.
  4. It influences inbound path choice and is propagated to all external peers

Explanation

LOCAL_PREF is a well-known discretionary attribute that tells routers inside one AS which exit point to prefer for outbound traffic. It is not sent to eBGP peers, so it stays local to the autonomous system.

Question 11BGP Fundamentals and Protocol Operation

An engineer wants to influence which entry point neighboring autonomous systems use to reach a prefix, without relying on AS_PATH prepending. Which attribute is designed for this purpose?

  1. Multi-Exit Discriminator Correct answer.
  2. ORIGIN
  3. NEXT_HOP
  4. LOCAL_PREF

Explanation

MED is an optional non-transitive attribute that suggests a preferred entry point into an AS when multiple connections exist. It is typically compared only between routes from the same neighboring AS.

Question 12BGP Fundamentals and Protocol Operation

Which statement correctly describes the difference between eBGP and iBGP peering?

  1. eBGP peers must be directly connected, while iBGP peers must also be directly connected
  2. iBGP prepends the local AS number, while eBGP does not
  3. eBGP uses TCP while iBGP uses UDP
  4. eBGP peers are in different autonomous systems, while iBGP peers share the same AS number Correct answer.

Explanation

The defining difference is administrative: eBGP sessions connect routers in different autonomous systems, and iBGP sessions connect routers within the same AS. Both use TCP port 179, and AS_PATH prepending occurs when advertising to eBGP peers.

Question 13BGP Fundamentals and Protocol Operation

What happens to a route when the BGP hold timer expires because no KEEPALIVE or UPDATE was received from the peer?

  1. The hold timer is automatically doubled
  2. The session is reset and routes learned from that peer are withdrawn Correct answer.
  3. The peer is placed in OpenSent state without dropping routes
  4. The route is retained but marked as stale indefinitely

Explanation

The hold timer defines the maximum interval without a KEEPALIVE or UPDATE before the peer is declared dead. When it expires, the session is torn down and the associated routes are removed from the RIB.

Question 14BGP Fundamentals and Protocol Operation

Which BGP message is used to withdraw a previously advertised prefix?

  1. KEEPALIVE
  2. NOTIFICATION
  3. OPEN
  4. UPDATE Correct answer.

Explanation

Withdrawals are carried in the UPDATE message, whose withdrawn-routes field lists prefixes no longer reachable. No separate withdraw message type exists in BGP.

Question 15BGP Fundamentals and Protocol Operation

A route reflector receives an iBGP route from one of its clients. To which peers does it reflect the route by default?

  1. To all other clients and to non-client iBGP peers Correct answer.
  2. To no peers unless next-hop-self is configured
  3. Only to eBGP peers
  4. Only back to the originating client

Explanation

A route reflector reflects routes from a client to all other clients and to non-client peers, while routes from non-clients go only to clients. This preserves the split-horizon rule while avoiding a full iBGP mesh.

Question 16BGP Fundamentals and Protocol Operation

What is the function of the BGP NOTIFICATION message?

  1. It requests a full routing table refresh
  2. It announces a new best path to peers
  3. It signals an error condition and causes the session to be closed Correct answer.
  4. It confirms receipt of an OPEN message

Explanation

A NOTIFICATION carries an error code and subcode and is the mechanism for orderly session teardown when a protocol error occurs. After sending or receiving it, the speaker returns to Idle.

Question 17BGP Fundamentals and Protocol Operation

Which attribute is used by a BGP speaker to tag routes so that they can be identified and acted upon by routing policy across multiple autonomous systems?

  1. ORIGIN
  2. NEXT_HOP
  3. COMMUNITY Correct answer.
  4. ATOMIC_AGGREGATE

Explanation

COMMUNITY is an optional transitive attribute carrying 32-bit tags that policy can match to set preferences, filter, or redistribute. Because it is transitive, communities can be propagated across AS boundaries.

Question 18BGP Fundamentals and Protocol Operation

A network engineer configures a static route to a null interface and redistributes it into BGP to prevent a prefix from being used. Which term describes this technique?

  1. Route reflection
  2. Route dampening
  3. Route blackholing Correct answer.
  4. Route summarization

Explanation

Advertising a prefix with a next hop pointing to a discard interface causes traffic for that prefix to be dropped, which is known as blackholing. It is commonly used for remote-triggered blackhole filtering with communities.

Question 19BGP Fundamentals and Protocol Operation

Which of the following best explains why BGP uses a path-vector design rather than a pure distance-vector design?

  1. It relies on hop count as the only metric
  2. It carries the full AS-level path, allowing loop detection and policy-based path selection Correct answer.
  3. It computes the shortest path using link-state flooding
  4. It requires every router to maintain a complete topology database

Explanation

Path-vector protocols advertise the sequence of autonomous systems a route traversed, so each speaker can detect loops and apply policy based on the AS path. This differs from distance-vector, which advertises only a metric, and from link-state, which floods topology.

Question 20BGP Fundamentals and Protocol Operation

After a BGP session is established, which state does the router enter when it has received a valid OPEN and is waiting for a KEEPALIVE from the peer?

  1. Idle
  2. Active
  3. Established
  4. OpenConfirm Correct answer.

Explanation

OpenConfirm is the intermediate state after a valid OPEN has been received and before the first KEEPALIVE arrives. Receipt of that KEEPALIVE moves the session to Established.

Question 21BGP Fundamentals and Protocol Operation

What is the primary role of the BGP OPEN message?

  1. It carries the withdrawn-routes list
  2. It negotiates session parameters such as AS number, hold time, and capabilities Correct answer.
  3. It advertises the initial routing table
  4. It acknowledges the TCP handshake

Explanation

The OPEN message carries the sender's AS number, hold time, BGP identifier, and optional capability parameters. Both peers must agree on these values before the session can proceed.

Question 22BGP Fundamentals and Protocol Operation

Which of the following is a valid reason to prefer an eBGP-learned route over an iBGP-learned route with otherwise equal attributes?

  1. eBGP routes have a lower ORIGIN value by default
  2. iBGP routes cannot be installed in the routing table
  3. The standard best-path algorithm prefers eBGP routes over iBGP routes Correct answer.
  4. iBGP routes always carry a longer AS_PATH

Explanation

After comparing LOCAL_PREF, AS_PATH length, ORIGIN, and MED, the algorithm prefers routes learned via eBGP over those learned via iBGP. This reflects the assumption that an external path is closer to the destination's own administrative domain.

Question 23BGP Fundamentals and Protocol Operation

Which BGP feature allows a router to reject routes that exceed a configured prefix threshold, protecting against a peer sending an excessive number of routes?

  1. Route dampening
  2. Maximum-prefix limit Correct answer.
  3. Next-hop-self
  4. Prefix suppression

Explanation

The maximum-prefix limit caps how many prefixes a neighbor may advertise; exceeding it can warn, or it can reset the session. It is a common safeguard against misconfiguration or route leaks.

Question 24BGP Fundamentals and Protocol Operation

In BGP, what does the ATOMIC_AGGREGATE attribute indicate?

  1. The advertising router aggregated more-specific routes and lost their detailed AS_PATH information Correct answer.
  2. The route is preferred over all non-aggregate routes
  3. The route has been blackholed by the originator
  4. The route must be discarded because it is malformed

Explanation

ATOMIC_AGGREGATE is a well-known discretionary attribute set when a router creates an aggregate without carrying the AS_PATH of the more-specific components. It warns downstream speakers that path information has been summarized.

Question 25BGP Fundamentals and Protocol Operation

What is the effect of configuring next-hop-self on an iBGP session?

  1. The router suppresses the NEXT_HOP attribute entirely
  2. The router rewrites the AS_PATH before advertising
  3. The router advertises itself as the next hop for routes it sends to the iBGP peer Correct answer.
  4. The router sets LOCAL_PREF to its own router ID

Explanation

next-hop-self causes the router to replace the NEXT_HOP of advertised routes with its own address on the iBGP session. This lets the peer resolve the next hop through the IGP without needing a route to the external address.

Question 26BGP Fundamentals and Protocol Operation

Which TCP port does a BGP speaker use by default when it initiates a session to a configured peer?

  1. 520
  2. 179 Correct answer.
  3. 89
  4. 646

Explanation

BGP runs over TCP and uses well-known port 179 as the listening and destination port for session establishment. Both peers must be able to reach each other on this port for the OPEN exchange to complete.

Question 27BGP Fundamentals and Protocol Operation

In the BGP finite state machine, which state indicates that the router has sent a TCP connection request and is waiting for the transport session to complete?

  1. Established
  2. OpenSent
  3. Active
  4. Connect Correct answer.

Explanation

Connect means BGP is actively trying to complete the TCP three-way handshake with the peer. Active is the state where the connection attempt failed or was refused and the router is listening and retrying, while OpenSent follows a completed TCP session.

Question 28BGP Fundamentals and Protocol Operation

A router has a single physical link to an external peer and receives a full internet table. An engineer wants the session to survive brief link glitches without tearing down the peering, while still detecting a genuinely dead peer. Which configuration approach achieves this?

  1. Increase the hold timer and scale the keepalive interval below it so transient outages are absorbed Correct answer.
  2. Decrease the keepalive interval to the minimum so failures are detected faster
  3. Disable keepalives entirely and rely on the IGP to detect peer failure
  4. Set the hold timer to zero on one side only so the other side enforces the timer

Explanation

The hold timer defines how long a speaker waits without a KEEPALIVE or UPDATE before declaring the peer down, and the negotiated value is the lower of the two peers' advertised hold times. Raising the hold timer while keeping the keepalive interval comfortably below it lets short interruptions pass without a session reset. The keepalive interval is typically one third of the hold time.

Question 29BGP Fundamentals and Protocol Operation

Two routers form an iBGP session across a transit network. The receiving router installs the advertised prefix but cannot forward traffic to it because the BGP next hop is unreachable in its IGP. Which statement explains the underlying rule?

  1. BGP does not resolve the next hop recursively unless the next-hop address is reachable through the routing table Correct answer.
  2. BGP rewrites the next hop of every iBGP route to the local loopback address by default
  3. BGP requires the next hop to be reachable only through a directly connected interface
  4. BGP discards iBGP routes whose next hop belongs to a different autonomous system

Explanation

A BGP route is only usable when the next-hop address can be resolved recursively through the routing table, typically via an IGP route or a connected network. If the advertising router's next hop is not reachable, the route stays in the BGP table but is not eligible for best-path selection or installation. Configuring next-hop-self on the advertising router or an IGP route to the next hop resolves the problem.

Question 30BGP Fundamentals and Protocol Operation

A service provider wants to confirm that a prefix will be accepted by a neighboring AS that applies strict prefix filtering. Which BGP mechanism lets the receiving AS publish, in machine-readable form, the exact prefixes and AS paths it will accept from each peer?

  1. A route target extended community attached to the prefix
  2. An IRR route object published in a routing registry Correct answer.
  3. A communities attribute listing the accepted prefixes
  4. An outbound route filter sent in the OPEN message

Explanation

Internet Routing Registries hold route objects that record which origin AS is authorized to announce a given prefix, and operators build prefix and origin filters from that data. Publishing a correct route object is how an announcement becomes verifiable and acceptable to peers that enforce registry-based filtering.

Question 31BGP Sessions, Peering Types, and Transport

In a Nokia SR OS CLI session, which command displays the current BGP neighbor session state for a specific peer?

  1. show router bgp peer-statistics
  2. show router bgp neighbor 192.0.2.1 Correct answer.
  3. show router bgp routes
  4. show router bgp summary

Explanation

The neighbor form of the BGP show command returns detailed per-peer information including the session state, timers, and negotiated capabilities for that specific address. The summary form lists all peers in a table but does not give the detailed per-peer view.

Question 32BGP Sessions, Peering Types, and Transport

Which TCP port does a BGP session use by default when no explicit port is configured?

  1. 179 Correct answer.
  2. 89
  3. 830
  4. 646

Explanation

BGP uses TCP port 179 as the well-known listening port for the session. Both the OPEN message exchange and the subsequent session traffic ride on this TCP connection, so any ACL or filter between peers must permit it.

Question 33BGP Sessions, Peering Types, and Transport

Two routers are directly connected but the BGP session remains in Active state. Which condition most directly explains this state?

  1. The local router is initiating TCP but no connection is being established Correct answer.
  2. The router is waiting for a keepalive timer to expire
  3. The peer has sent a NOTIFICATION and the session is closing
  4. The session is fully established and exchanging routes

Explanation

Active means the local router is actively trying to open the TCP connection to the peer but the three-way handshake has not completed. Common causes are reachability problems, a missing or wrong neighbor address, or a filter blocking TCP 179.

Question 34BGP Sessions, Peering Types, and Transport

What is the primary purpose of the BGP OPEN message?

  1. To acknowledge receipt of the previous UPDATE message
  2. To request a full routing table refresh from the peer
  3. To advertise the first batch of prefixes for the session
  4. To negotiate capabilities and exchange the AS number and hold time before any routes are sent Correct answer.

Explanation

The OPEN message carries the version, local AS number, hold time, BGP identifier, and optional capability parameters. Both sides must agree on these parameters before the session can move to Established and routes can be exchanged.

Question 35BGP Sessions, Peering Types, and Transport

An eBGP session is being configured between two directly connected routers in different autonomous systems. Which statement about the default eBGP behavior is correct?

  1. The peer must be reachable over a directly connected link unless multihop is configured Correct answer.
  2. The session requires an IGP to be running between the peers
  3. The peer can be multiple hops away by default
  4. The session uses UDP as its transport

Explanation

eBGP assumes a single IP hop between peers by default, so the TTL on the TCP connection is set to 1. Reaching a peer across multiple hops requires explicitly configuring multihop and adjusting the TTL.

Question 36BGP Sessions, Peering Types, and Transport

Which statement best describes an iBGP session between two routers in the same autonomous system?

  1. It always rewrites the next hop to the local interface address
  2. It does not change the next hop by default when advertising routes learned from an eBGP peer Correct answer.
  3. It requires the peers to be directly connected
  4. It uses a different TCP port than eBGP

Explanation

iBGP preserves the next hop learned from eBGP so that other iBGP speakers can reach the external destination through the correct exit point. This is why an IGP must provide reachability to that next hop inside the AS.

Question 37BGP Sessions, Peering Types, and Transport

A router running Nokia SR OS has two iBGP peers and learns a route from one of them. What does the default iBGP split-horizon rule require?

  1. The route is advertised to all iBGP peers immediately
  2. The route is not advertised to the other iBGP peer Correct answer.
  3. The route is advertised only after a route reflector is configured
  4. The route is advertised only if the next hop is reachable

Explanation

By default, a route learned from an iBGP peer is not re-advertised to another iBGP peer, which prevents routing loops inside the AS. Full-mesh iBGP or a route reflector is needed to distribute such routes to all speakers.

Question 38BGP Sessions, Peering Types, and Transport

Which Nokia SR OS command is used to configure a BGP group and assign it a peer AS number?

  1. configure router bgp group "ebgp-peers" local-as 65001
  2. configure router bgp neighbor 192.0.2.1 peer-as 65001
  3. configure router bgp group "ebgp-peers" peer-as 65001 Correct answer.
  4. configure router bgp group "ebgp-peers" export "bgp-out"

Explanation

The group context holds shared peer parameters such as peer-as, which is inherited by neighbors configured within that group. Setting peer-as on the group avoids repeating it for every neighbor in the group.

Question 39BGP Sessions, Peering Types, and Transport

What is the effect of configuring multihop on an eBGP session in Nokia SR OS?

  1. It allows the session to be established with a peer that is not directly connected by raising the TTL Correct answer.
  2. It enables route reflection for the peer
  3. It disables the BGP hold timer
  4. It converts the session to iBGP

Explanation

The multihop parameter increases the TTL used for the TCP connection so the eBGP session can span multiple IP hops. It is typically combined with a static route or IGP reachability to the peer loopback address.

Question 40BGP Sessions, Peering Types, and Transport

A BGP session is flapping repeatedly and the router is applying dampening-like suppression. Which mechanism is designed to limit how often a peer can re-establish a session after repeated failures?

  1. BGP graceful restart
  2. BGP session damping or peer flap damping Correct answer.
  3. BGP route refresh
  4. BGP hold timer

Explanation

Peer flap damping penalizes a neighbor that repeatedly resets its session, delaying reconnection attempts. This prevents unstable peers from continuously consuming CPU and destabilizing routing.

Question 41BGP Sessions, Peering Types, and Transport

Which statement about the BGP hold timer and keepalive timer is correct?

  1. The keepalive interval must equal the hold time
  2. The keepalive timer is only used on iBGP sessions
  3. The hold timer is always 180 seconds and cannot be negotiated
  4. The keepalive interval is typically one third of the negotiated hold time Correct answer.

Explanation

The negotiated hold time determines how long a peer waits without a keepalive before declaring the session down, and the keepalive is normally sent at one third of that value. This gives two chances to miss a keepalive before the hold timer expires.

Question 42BGP Sessions, Peering Types, and Transport

An operator wants a BGP session to survive a control-plane restart without dropping forwarding entries. Which capability should be enabled on both peers?

  1. Graceful restart Correct answer.
  2. Route reflection
  3. Confederation
  4. Multihop

Explanation

Graceful restart allows a router to signal a planned restart so peers retain routes and forwarding state during the interruption. When the session returns, the peers exchange routing information and converge without a full traffic outage.

Question 43BGP Sessions, Peering Types, and Transport

Which BGP message is used to tear down an established session when an error condition such as a hold-timer expiry is detected?

  1. NOTIFICATION Correct answer.
  2. OPEN
  3. UPDATE
  4. KEEPALIVE

Explanation

The NOTIFICATION message carries an error code and subcode and is the last message sent before the session closes. It tells the peer exactly why the session is being terminated.

Question 44BGP Sessions, Peering Types, and Transport

What is the purpose of configuring a BGP peer group in Nokia SR OS?

  1. To enable multihop automatically for every neighbor
  2. To force all peers into the same autonomous system
  3. To apply shared parameters and policies to multiple neighbors with a single configuration block Correct answer.
  4. To create a separate routing instance for each peer

Explanation

A group lets common attributes such as peer-as, timers, and import/export policies be defined once and inherited by all neighbors in the group. This reduces configuration size and the chance of inconsistent settings.

Question 45BGP Sessions, Peering Types, and Transport

A Nokia SR OS router has two eBGP peers to the same external AS and receives the same prefix from both. Which attribute does BGP evaluate first in the best-path selection process?

  1. Local preference Correct answer.
  2. AS path length
  3. MED
  4. Weight

Explanation

Among the listed attributes, Nokia SR OS evaluates local preference before AS path length and MED, preferring the higher local preference. The documented Nokia decision sequence does not use Cisco-style weight ahead of local preference.

Question 46BGP Sessions, Peering Types, and Transport

Which statement about the BGP identifier (router ID) is correct?

  1. It must match the peer's router ID for the session to come up
  2. It is only used on eBGP sessions
  3. It must be a unique 32-bit value within the AS and is carried in the OPEN message Correct answer.
  4. It is always the lowest interface address on the router

Explanation

The BGP identifier is a 32-bit value, typically formatted as an IPv4 address, that uniquely identifies the speaker within the AS. It is included in the OPEN message and used in route selection and loop detection.

Question 47BGP Sessions, Peering Types, and Transport

An operator configures an iBGP session between two loopback addresses. Which requirement must be met for the session to establish?

  1. The loopbacks must be in the same subnet
  2. The routers must be in different autonomous systems
  3. The session must use multihop with a TTL of 255
  4. Each router must have a route to the other's loopback address Correct answer.

Explanation

iBGP sessions between loopbacks require IP reachability to the peer loopback, usually provided by an IGP or static route. Without that reachability the TCP connection cannot be established and the session stays in Active.

Question 48BGP Sessions, Peering Types, and Transport

Which mechanism allows a single router to reflect iBGP routes to multiple clients, avoiding a full mesh?

  1. Confederation
  2. Multihop
  3. Route reflector Correct answer.
  4. Graceful restart

Explanation

A route reflector relaxes the iBGP split-horizon rule by reflecting routes between clients and non-clients. This removes the need for every iBGP speaker to peer with every other speaker.

Question 49BGP Sessions, Peering Types, and Transport

A customer edge router peers with a provider using a private AS number. Which BGP feature prevents the private AS from appearing in the global table?

  1. MED
  2. next-hop-self
  3. as-path remove-private Correct answer.
  4. local-preference

Explanation

The remove-private option strips private AS numbers from the AS path before advertising the route to external peers. This keeps private AS numbers out of the global routing table as required by convention.

Question 50BGP Sessions, Peering Types, and Transport

Which statement about BGP confederations is correct?

  1. They replace the need for any iBGP peering
  2. They eliminate the need for route reflectors in all designs
  3. They are used only between different autonomous systems
  4. They divide a large AS into sub-ASes that peer internally while presenting one AS to the outside Correct answer.

Explanation

A confederation splits an AS into smaller sub-ASes, each running iBGP internally, with eBGP-like sessions between sub-ASes. To external peers the entire confederation appears as a single AS number.