BGP practice questions

An enterprise network has two routers, R1 and R2, both running BGP. R1 is an eBGP speaker with ISP1, and R2 is an eBGP speaker with ISP2. Both routers are in the same AS 65000. The engineer wants to ensure that traffic from the enterprise to the Internet prefers the path through ISP1 when both links are up. R1 learns a default route from ISP1, and R2 learns a default route from ISP2. Which BGP attribute should the engineer modify on R1 to influence outbound traffic selection?

Trap 1: Set a lower MED on R1 for the default route learned from ISP1.

Incorrect because MED is used to influence inbound traffic from neighboring ASes, not outbound traffic from within the AS.

Trap 2: Prepend AS 65000 multiple times on R2's updates to ISP2.

Incorrect because AS_PATH prepending affects inbound traffic from ISP2, not outbound traffic from the enterprise.

Trap 3: Configure a community on R1 to mark the default route as no-export.

Incorrect because the no-export community prevents the route from being advertised to eBGP peers, but does not influence outbound path selection within the AS.

A
Set a higher local preference on R1 for the default route learned from ISP1.
Correct because local preference influences outbound path selection within the AS; a higher value makes the route more preferred.
B
Set a lower MED on R1 for the default route learned from ISP1.
Why wrong: Incorrect because MED is used to influence inbound traffic from neighboring ASes, not outbound traffic from within the AS.
C
Prepend AS 65000 multiple times on R2's updates to ISP2.
Why wrong: Incorrect because AS_PATH prepending affects inbound traffic from ISP2, not outbound traffic from the enterprise.
D
Configure a community on R1 to mark the default route as no-export.
Why wrong: Incorrect because the no-export community prevents the route from being advertised to eBGP peers, but does not influence outbound path selection within the AS.

Question 2mediummultiple choice

A network engineer is troubleshooting BGP peering between two routers in different autonomous systems. The peering is established over a directly connected Ethernet link. The engineer notices that the BGP session is flapping every few minutes. The configuration on both routers appears correct, and the IP connectivity is stable. The engineer checks the BGP logs and sees messages like 'BGP-3-NOTIFICATION: sent 4/0 (Hold Timer Expired)'. What is the most likely cause of this issue?

Trap 1: The MTU on the link is mismatched, causing BGP packets to be…

Incorrect because MTU mismatch typically causes packet drops or failure to establish the session, not hold timer expiry.

Trap 2: The TTL for eBGP is set to 1, and the routers are not directly…

Incorrect because the scenario states they are directly connected, so TTL=1 is fine; TTL issues would prevent session establishment, not cause hold timer expiry.

Trap 3: The BGP update timer is set too high, causing delays in sending…

Incorrect because update timers do not affect keepalive messages; hold timer expiry is related to keepalive frequency, not update frequency.

A
The hold timer values are mismatched between the two routers.
Correct because a hold timer mismatch causes the router with the smaller hold time to expire, leading to session flaps.
B
The MTU on the link is mismatched, causing BGP packets to be fragmented.
Why wrong: Incorrect because MTU mismatch typically causes packet drops or failure to establish the session, not hold timer expiry.
C
The TTL for eBGP is set to 1, and the routers are not directly connected.
Why wrong: Incorrect because the scenario states they are directly connected, so TTL=1 is fine; TTL issues would prevent session establishment, not cause hold timer expiry.
D
The BGP update timer is set too high, causing delays in sending updates.
Why wrong: Incorrect because update timers do not affect keepalive messages; hold timer expiry is related to keepalive frequency, not update frequency.

Question 3hardmultiple choice

A network engineer is configuring BGP on a Cisco router that is part of an enterprise network with multiple BGP peers. The router receives routes from two different ISPs. The engineer wants to ensure that only specific prefixes from ISP-A are installed in the routing table, while all other routes from ISP-A are ignored. Additionally, the engineer wants to accept all routes from ISP-B. Which BGP feature should be used on the router for the peering with ISP-A?

Trap 1: Configure a network statement under BGP for the desired prefixes.

Incorrect because network statements are used to advertise routes into BGP, not to filter incoming routes.

Trap 2: Use the default-information originate command under BGP.

Incorrect because this command is used to generate a default route, not to filter incoming prefixes.

Trap 3: Apply a route map to the neighbor using the route-map command in…

Incorrect because while a route map can filter, the scenario specifically mentions prefix-based filtering; a distribute list is more direct and simpler for this task.

A
Apply a distribute list under the BGP neighbor configuration for ISP-A.
Correct because a distribute list with a prefix list can filter incoming routes based on prefix, allowing only specific prefixes.
B
Configure a network statement under BGP for the desired prefixes.
Why wrong: Incorrect because network statements are used to advertise routes into BGP, not to filter incoming routes.
C
Use the default-information originate command under BGP.
Why wrong: Incorrect because this command is used to generate a default route, not to filter incoming prefixes.
D
Apply a route map to the neighbor using the route-map command in the inbound direction.
Why wrong: Incorrect because while a route map can filter, the scenario specifically mentions prefix-based filtering; a distribute list is more direct and simpler for this task.

Question 4hardmultiple choice

An enterprise has two BGP routers, R1 and R2, both in AS 65000. R1 peers with ISP1 (AS 100) and R2 peers with ISP2 (AS 200). The enterprise advertises a prefix 192.168.0.0/24 to both ISPs. The engineer wants to ensure that traffic from the Internet to this prefix enters the network primarily via R1, and only uses R2 if the link to ISP1 fails. Which BGP attribute should be manipulated on the updates sent to the ISPs?

Trap 1: Set a higher MED on R1's updates to ISP1.

Incorrect because MED is only compared within the same AS; ISP1 and ISP2 are different ASes, so MED from R1 will not influence ISP2's path selection.

Trap 2: Set a higher local preference on R1 for routes learned from ISP1.

Incorrect because local preference influences outbound traffic from the enterprise, not inbound traffic from the Internet.

Trap 3: Use the no-export community on R1's updates to ISP1.

Incorrect because the no-export community prevents the route from being advertised to eBGP peers, which would stop ISP1 from advertising the prefix, not influence path selection.

A
Prepend AS 65000 multiple times on R2's updates to ISP2.
Correct because AS_PATH prepending makes the path through R2 longer, so ISP2 will prefer the path through ISP1, directing traffic to R1.
B
Set a higher MED on R1's updates to ISP1.
Why wrong: Incorrect because MED is only compared within the same AS; ISP1 and ISP2 are different ASes, so MED from R1 will not influence ISP2's path selection.
C
Set a higher local preference on R1 for routes learned from ISP1.
Why wrong: Incorrect because local preference influences outbound traffic from the enterprise, not inbound traffic from the Internet.
D
Use the no-export community on R1's updates to ISP1.
Why wrong: Incorrect because the no-export community prevents the route from being advertised to eBGP peers, which would stop ISP1 from advertising the prefix, not influence path selection.

Question 5mediummultiple choice

A network engineer is configuring BGP on a Cisco router that connects to two ISPs. The router has a default route pointing to each ISP. The engineer wants to load balance outbound traffic across both ISPs. The router receives a default route from both ISPs. Which BGP configuration approach will allow the router to install both default routes in the routing table and load balance traffic?

Trap 1: Configure the network command to advertise the default route from…

Incorrect because the network command is used to originate routes, not to load balance incoming routes.

Trap 2: Set the local preference to the same value on both default routes.

Incorrect because local preference is used for path selection, but even if equal, BGP still picks only one best path unless multipath is configured.

Trap 3: Use the redistribute command to redistribute the default routes…

Incorrect because redistribution is not needed; the routes are already learned via BGP, and redistribution does not enable load balancing.

A
Configure the maximum-paths command under the BGP address family and use the bgp bestpath as-path multipath-relax command.
Correct because maximum-paths allows multiple paths to be installed, and multipath-relax ignores AS_PATH length differences, enabling load balancing across different ASes.
B
Configure the network command to advertise the default route from both ISPs.
Why wrong: Incorrect because the network command is used to originate routes, not to load balance incoming routes.
C
Set the local preference to the same value on both default routes.
Why wrong: Incorrect because local preference is used for path selection, but even if equal, BGP still picks only one best path unless multipath is configured.
D
Use the redistribute command to redistribute the default routes into BGP.
Why wrong: Incorrect because redistribution is not needed; the routes are already learned via BGP, and redistribution does not enable load balancing.

Question 6hardmultiple choice

An engineer is configuring BGP on a router that will act as a route reflector to reduce iBGP peering requirements. The router has several iBGP peers. The engineer wants to ensure that the route reflector does not modify the next-hop attribute of routes it reflects to its clients. Which configuration command should the engineer use?

Trap 1: Configure 'no bgp next-hop-self' under the BGP address family for…

Incorrect because 'no bgp next-hop-self' is not a valid command; the correct command is 'no neighbor next-hop-self', but that only removes the configuration that would set next-hop to self; it does not guarantee the next-hop is unchanged if other mechanisms are in place.

Trap 2: Configure 'bgp route-reflector' under the BGP address family.

Incorrect because 'bgp route-reflector' is not a valid command; the correct command is 'bgp route-reflector' is not used; route reflection is enabled with 'neighbor route-reflector-client'.

Trap 3: Configure 'neighbor next-hop-self' on the route reflector for its…

Incorrect because this command would cause the route reflector to set itself as the next-hop, modifying the attribute, which is the opposite of what the engineer wants.

A
Configure 'neighbor next-hop-unchanged' under the BGP address family for the route reflector clients.
Correct because this command explicitly instructs the router to not modify the next-hop attribute when sending routes to the specified neighbor, preserving the original next-hop.
B
Configure 'no bgp next-hop-self' under the BGP address family for the route reflector clients.
Why wrong: Incorrect because 'no bgp next-hop-self' is not a valid command; the correct command is 'no neighbor next-hop-self', but that only removes the configuration that would set next-hop to self; it does not guarantee the next-hop is unchanged if other mechanisms are in place.
C
Configure 'bgp route-reflector' under the BGP address family.
Why wrong: Incorrect because 'bgp route-reflector' is not a valid command; the correct command is 'bgp route-reflector' is not used; route reflection is enabled with 'neighbor route-reflector-client'.
D
Configure 'neighbor next-hop-self' on the route reflector for its clients.
Why wrong: Incorrect because this command would cause the route reflector to set itself as the next-hop, modifying the attribute, which is the opposite of what the engineer wants.

Question 7hardmultiple choice

A network engineer is troubleshooting a BGP issue where a router is not installing a specific prefix in its routing table, even though the prefix is present in the BGP table. The engineer runs 'show ip bgp 10.0.0.0/24' and sees that the route is valid but not best. The BGP table shows that the route has a higher local preference than the current best path, but the AS_PATH is longer. What is the most likely reason the route is not being selected as best?

Trap 1: The route with higher local preference has a higher MED value.

Incorrect because MED is checked after AS_PATH length; since local preference is higher, it would be preferred before considering MED.

Trap 2: The route with higher local preference is not synchronized with IGP.

Incorrect because BGP synchronization is disabled by default and is rarely used; even if enabled, it would cause the route to be invalid, not just not best.

Trap 3: The route with higher local preference was learned from an eBGP…

Incorrect because eBGP routes are preferred over iBGP routes (all else equal), but local preference is checked before the source of the route (eBGP vs iBGP).

A
The route with higher local preference has a lower weight than the current best path.
Correct because weight is checked before local preference in BGP path selection; a higher weight on the current best path would make it preferred even if local preference is lower.
B
The route with higher local preference has a higher MED value.
Why wrong: Incorrect because MED is checked after AS_PATH length; since local preference is higher, it would be preferred before considering MED.
C
The route with higher local preference is not synchronized with IGP.
Why wrong: Incorrect because BGP synchronization is disabled by default and is rarely used; even if enabled, it would cause the route to be invalid, not just not best.
D
The route with higher local preference was learned from an eBGP peer, while the current best path is from an iBGP peer.
Why wrong: Incorrect because eBGP routes are preferred over iBGP routes (all else equal), but local preference is checked before the source of the route (eBGP vs iBGP).

Question 8mediummultiple choice

An enterprise network uses BGP to connect to two ISPs. The router has a BGP configuration that includes the command 'bgp bestpath med missing-as-worst'. The engineer notices that routes from ISP-A that do not have the MED attribute are being preferred over routes from ISP-B that have a MED of 50. What is the effect of the 'bgp bestpath med missing-as-worst' command?

Trap 1: It causes routes without the MED attribute to be treated as having…

Incorrect because that is the default behavior without the command; the command changes the default to treat missing MED as worst.

Trap 2: It causes routes with the MED attribute to be ignored during path…

Incorrect because the command only affects how missing MED is treated; it does not ignore MED for routes that have it.

Trap 3: It causes the router to add a MED value of 0 to all routes that are…

Incorrect because the command does not add a MED value; it only influences the comparison logic.

A
It causes routes without the MED attribute to be treated as having the highest MED value, making them less preferred.
Correct because the command sets missing MED to the worst possible value, which is the highest MED, making those routes less preferred in path selection.
B
It causes routes without the MED attribute to be treated as having a MED value of 0, making them more preferred.
Why wrong: Incorrect because that is the default behavior without the command; the command changes the default to treat missing MED as worst.
C
It causes routes with the MED attribute to be ignored during path selection.
Why wrong: Incorrect because the command only affects how missing MED is treated; it does not ignore MED for routes that have it.
D
It causes the router to add a MED value of 0 to all routes that are missing MED.
Why wrong: Incorrect because the command does not add a MED value; it only influences the comparison logic.

Question 9easymultiple choice

A network engineer is configuring BGP on a router that will be used for BGP route summarization. The router receives multiple more-specific prefixes from its eBGP peers. The engineer wants to advertise a summary route to the iBGP peers without advertising the more-specific routes. Which command should the engineer use to suppress the more-specific routes while still installing them in the local routing table?

Trap 1: Use the 'network' command to advertise the summary route.

Incorrect because the 'network' command advertises an exact prefix from the routing table, but does not suppress more-specific routes.

Trap 2: Use the 'summary-address' command under the BGP address family.

Incorrect because 'summary-address' is not a valid BGP command; the correct command is 'aggregate-address'.

Trap 3: Use the 'redistribute' command to inject the summary route into BGP.

Incorrect because redistribution does not provide suppression of more-specific routes; it would advertise the summary route but not automatically suppress others.

A
Use the 'aggregate-address' command with the 'summary-only' keyword.
Correct because this command creates an aggregate route and suppresses the advertisement of more-specific routes to BGP peers.
B
Use the 'network' command to advertise the summary route.
Why wrong: Incorrect because the 'network' command advertises an exact prefix from the routing table, but does not suppress more-specific routes.
C
Use the 'summary-address' command under the BGP address family.
Why wrong: Incorrect because 'summary-address' is not a valid BGP command; the correct command is 'aggregate-address'.
D
Use the 'redistribute' command to inject the summary route into BGP.
Why wrong: Incorrect because redistribution does not provide suppression of more-specific routes; it would advertise the summary route but not automatically suppress others.

Question 10mediummultiple choice

A network engineer runs the following command on Router R1:

R1# show bgp summary

BGP router identifier 10.0.0.1, local AS number 65001 BGP table version is 14, main routing table version 14 4 network entries using 1152 bytes of memory 4 path entries using 320 bytes of memory 2/1 BGP path/bestpath attribute entries using 560 bytes of memory 0 BGP route reflector client to client reflections 2 BGP community entries using 80 bytes of memory

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
10.0.1.2        4        65002    2345    2346       14    0    0 00:12:34        3
10.0.1.3        4        65003    1234    1235       14    0    0 00:08:21        2
10.0.1.4        4        65004     567     568       14    0    0 00:05:45        0

Based on this output, what can be concluded?

Trap 1: Neighbor 10.0.1.4 is in the 'Active' state because it received 0…

The output shows '0' in the State/PfxRcd column, which indicates the session is established (no state word) but 0 prefixes received. 'Active' would show the word 'Active' instead of a number.

Trap 2: Neighbor 10.0.1.4 has sent 0 prefixes to R1.

The column is 'State/PfxRcd' which means prefixes received, not sent. The number 0 indicates R1 received 0 prefixes from 10.0.1.4.

Trap 3: The BGP session with 10.0.1.4 is down.

If the session were down, the state would show 'Idle', 'Active', 'Connect', etc. The presence of a number (0) indicates the session is established.

A
Neighbor 10.0.1.4 is in the 'Active' state because it received 0 prefixes.
Why wrong: The output shows '0' in the State/PfxRcd column, which indicates the session is established (no state word) but 0 prefixes received. 'Active' would show the word 'Active' instead of a number.
B
Neighbor 10.0.1.4 has sent 0 prefixes to R1.
Why wrong: The column is 'State/PfxRcd' which means prefixes received, not sent. The number 0 indicates R1 received 0 prefixes from 10.0.1.4.
C
Neighbor 10.0.1.4 is not advertising any prefixes to R1.
The 0 in the PfxRcd column means R1 has received no prefixes from 10.0.1.4. This is likely because 10.0.1.4 has no routes to advertise or is filtering outbound.
D
The BGP session with 10.0.1.4 is down.
Why wrong: If the session were down, the state would show 'Idle', 'Active', 'Connect', etc. The presence of a number (0) indicates the session is established.

Question 11mediummultiple choice

A network engineer runs the following command on Router R1:

R1# show bgp ipv4 unicast 192.168.1.0

BGP routing table entry for 192.168.1.0/24, version 10 Paths: (2 available, best #2, table default) Advertised to update-groups: 1 Refresh Epoch 1 Local

10.0.0.2 from 10.0.1.2 (10.0.0.2)

Origin IGP, metric 0, localpref 100, valid, internal rx pathid: 0, tx pathid: 0x0 Local, (received & used)

10.0.0.3 from 10.0.1.3 (10.0.0.3)

Origin IGP, metric 0, localpref 200, valid, internal, best rx pathid: 0, tx pathid: 0x0

Based on this output, what can be concluded?

Trap 1: The path from 10.0.1.2 is the best path because it is received…

BGP does not select best path based on order received. The best path is path #2 from 10.0.1.3 due to higher local preference.

Trap 2: Both paths are from external BGP peers.

Both paths show 'internal' in the output, indicating they are iBGP routes, not eBGP.

Trap 3: The path from 10.0.1.2 is marked as best because it has a lower…

Both paths have metric 0. The best path is determined by local preference, not metric.

A
The path from 10.0.1.2 is the best path because it is received first.
Why wrong: BGP does not select best path based on order received. The best path is path #2 from 10.0.1.3 due to higher local preference.
B
The path from 10.0.1.3 is preferred because of a higher local preference.
Local preference is 200 for path #2 (from 10.0.1.3) versus 100 for path #1. Higher local preference is preferred in BGP best path selection.
C
Both paths are from external BGP peers.
Why wrong: Both paths show 'internal' in the output, indicating they are iBGP routes, not eBGP.
D
The path from 10.0.1.2 is marked as best because it has a lower metric.
Why wrong: Both paths have metric 0. The best path is determined by local preference, not metric.

Question 12easymultiple choice

A network engineer runs the following command on Router R1:

R1# show bgp ipv4 unicast summary | include 10.0.1.5
10.0.1.5        4        65005    3456    3457       15    0    0 00:15:22        5

Based on this output, what can be concluded?

Trap 1: The BGP session with 10.0.1.5 has been down for 15 minutes and 22…

The 'Up/Down' column shows the time since the session was established or the state changed. A format like 00:15:22 indicates uptime, not downtime.

Trap 2: The BGP session with 10.0.1.5 is in the 'Active' state.

If the session were in Active state, the output would show the word 'Active' instead of a number.

Trap 3: The BGP session with 10.0.1.5 has sent 5 prefixes.

The column is 'State/PfxRcd' which indicates prefixes received, not sent.

A
The BGP session with 10.0.1.5 has been down for 15 minutes and 22 seconds.
Why wrong: The 'Up/Down' column shows the time since the session was established or the state changed. A format like 00:15:22 indicates uptime, not downtime.
B
The BGP session with 10.0.1.5 is up and has received 5 prefixes.
The number 5 in the State/PfxRcd column indicates 5 prefixes received, and the lack of a state word means the session is established.
C
The BGP session with 10.0.1.5 is in the 'Active' state.
Why wrong: If the session were in Active state, the output would show the word 'Active' instead of a number.
D
The BGP session with 10.0.1.5 has sent 5 prefixes.
Why wrong: The column is 'State/PfxRcd' which indicates prefixes received, not sent.

Question 13hardmultiple choice

A network engineer runs the following command on Router R1:

R1# show bgp ipv4 unicast 10.10.10.0

BGP routing table entry for 10.10.10.0/24, version 20 Paths: (2 available, best #1, table default) Advertised to update-groups: 1 Refresh Epoch 1 65050 65100

10.0.1.2 from 10.0.1.2 (10.0.0.2)

Origin IGP, metric 0, localpref 100, weight 0, valid, external, best rx pathid: 0, tx pathid: 0x0 65050 65100 65200

10.0.1.3 from 10.0.1.3 (10.0.0.3)

Origin IGP, metric 0, localpref 100, weight 0, valid, external rx pathid: 0, tx pathid: 0x0

Based on this output, what can be concluded?

Trap 1: Path #2 is the best path because it has a longer AS_PATH,…

BGP prefers shorter AS_PATH, not longer. Longer AS_PATH is less preferred.

Trap 2: Both paths are equally preferred, and BGP uses tie-breaking rules…

The paths are not equal because AS_PATH lengths differ. BGP does not proceed to tie-breaking when AS_PATH is different.

Trap 3: Path #1 is the best path because it is received from a higher IP…

The best path selection is based on AS_PATH length, not neighbor IP address.

A
Path #2 is the best path because it has a longer AS_PATH, indicating more specific routing.
Why wrong: BGP prefers shorter AS_PATH, not longer. Longer AS_PATH is less preferred.
B
Path #1 is the best path because it has a shorter AS_PATH length.
Path #1 has AS_PATH length 2 (65050 65100) while path #2 has length 3 (65050 65100 65200). Shorter AS_PATH is preferred.
C
Both paths are equally preferred, and BGP uses tie-breaking rules like router ID.
Why wrong: The paths are not equal because AS_PATH lengths differ. BGP does not proceed to tie-breaking when AS_PATH is different.
D
Path #1 is the best path because it is received from a higher IP address.
Why wrong: The best path selection is based on AS_PATH length, not neighbor IP address.

Question 14mediummultiple choice

A network engineer runs the following command on Router R1:

R1# show bgp ipv4 unicast neighbors 10.0.1.2 received-routes

Network Next Hop Metric LocPrf Weight Path *> 192.168.1.0/24 10.0.1.2 0 100 0 65050 i *> 192.168.2.0/24 10.0.1.2 0 100 0 65050 i *> 10.10.10.0/24 10.0.1.2 0 100 0 65050 65100 i

Total number of prefixes 3

Based on this output, what can be concluded?

Trap 1: All three routes are installed in the routing table of R1.

The output shows received routes, not necessarily installed routes. The '>' indicates best path among received from this neighbor, but not that it is in the routing table.

Trap 2: R1 is advertising these three routes to neighbor 10.0.1.2.

This command shows received routes, not advertised routes. To see advertised routes, use 'advertised-routes'.

Trap 3: The route 10.10.10.0/24 has a weight of 0, meaning it is not…

Weight 0 is default. The '>' indicates it is the best path from this neighbor, but weight is not the sole determinant.

A
All three routes are installed in the routing table of R1.
Why wrong: The output shows received routes, not necessarily installed routes. The '>' indicates best path among received from this neighbor, but not that it is in the routing table.
B
R1 has received 3 prefixes from neighbor 10.0.1.2.
The command shows all routes received from the neighbor, and the total is 3 prefixes.
C
R1 is advertising these three routes to neighbor 10.0.1.2.
Why wrong: This command shows received routes, not advertised routes. To see advertised routes, use 'advertised-routes'.
D
The route 10.10.10.0/24 has a weight of 0, meaning it is not preferred.
Why wrong: Weight 0 is default. The '>' indicates it is the best path from this neighbor, but weight is not the sole determinant.

Question 15easymultiple choice

A network engineer runs the following command on Router R1:

R1# show bgp ipv4 unicast neighbors 10.0.1.2 advertised-routes

Network Next Hop Metric LocPrf Weight Path *> 172.16.0.0/16 10.0.1.1 0 100 0 i *> 172.16.1.0/24 10.0.1.1 0 100 0 i

Total number of prefixes 2

Based on this output, what can be concluded?

Trap 1: R1 is receiving 2 prefixes from neighbor 10.0.1.2.

This command shows advertised routes, not received routes. Received routes are shown with 'received-routes'.

Trap 2: Neighbor 10.0.1.2 is advertising these routes to R1.

The output is from R1's perspective, showing what R1 advertises, not what it receives.

Trap 3: The routes are being advertised with a next hop of 10.0.1.2.

The next hop shown is 10.0.1.1, which is R1's own interface IP, not the neighbor's.

A
R1 is receiving 2 prefixes from neighbor 10.0.1.2.
Why wrong: This command shows advertised routes, not received routes. Received routes are shown with 'received-routes'.
B
R1 is advertising 2 prefixes to neighbor 10.0.1.2.
The command explicitly shows routes that R1 advertises to the neighbor. The total is 2 prefixes.
C
Neighbor 10.0.1.2 is advertising these routes to R1.
Why wrong: The output is from R1's perspective, showing what R1 advertises, not what it receives.
D
The routes are being advertised with a next hop of 10.0.1.2.
Why wrong: The next hop shown is 10.0.1.1, which is R1's own interface IP, not the neighbor's.

Question 16easymultiple choice

A network engineer runs the following command on Router R1:

R1# show bgp ipv4 unicast 192.168.1.0/24

BGP routing table entry for 192.168.1.0/24, version 15 Paths: (1 available, best #1, table default) Advertised to update-groups: 1 Refresh Epoch 1 65050, (received & used)

10.0.1.2 from 10.0.1.2 (10.0.0.2)

Origin IGP, metric 0, localpref 100, weight 0, valid, external, best rx pathid: 0, tx pathid: 0x0

Based on this output, what can be concluded?

Trap 1: The route was learned from an internal BGP peer.

The output says 'external', meaning it is an eBGP route, not iBGP.

Trap 2: The route has a local preference of 0.

The local preference is 100, not 0.

Trap 3: The route is not valid because it is external.

The route is marked as 'valid', so it is valid.

A
The route was learned from an internal BGP peer.
Why wrong: The output says 'external', meaning it is an eBGP route, not iBGP.
B
The route is from AS 65050 and is the best path.
The AS_PATH shows 65050, and the path is marked as 'best'.
C
The route has a local preference of 0.
Why wrong: The local preference is 100, not 0.
D
The route is not valid because it is external.
Why wrong: The route is marked as 'valid', so it is valid.

Question 17hardmultiple choice

A network engineer runs the following command on Router R1:

R1# show bgp ipv4 unicast neighbors 10.0.1.2

BGP neighbor is 10.0.1.2, remote AS 65050, external link BGP version 4, remote router ID 10.0.0.2 BGP state = Established, up for 00:23:45 Last read 00:00:15, last write 00:00:10, hold time is 90, keepalive interval is 30 seconds

Neighbor sessions:

1 active, is not multisession capable

Neighbor capabilities:

Route refresh: advertised and received(new) Four-octets ASN: advertised and received Address family IPv4 Unicast: advertised and received Enhanced Refresh: advertised and received Multisession: advertised Message statistics: InQ depth is 0 OutQ depth is 0 Sent Rcvd Opens: 1 1 Notifications: 0 0 Updates: 5 3 Keepalives: 47 48 Route Refresh: 0 0 Total: 53 52 Default minimum time between advertisement runs is 30 seconds

Based on this output, what can be concluded?

Trap 1: The BGP session is in the 'Idle' state because the last read was 15…

The state is 'Established', not Idle. The last read time is normal for keepalive intervals.

Trap 2: The neighbor is an internal BGP peer because the remote AS is 65050.

The output says 'external link', so it is an eBGP peer. The remote AS being different from the local AS indicates eBGP.

Trap 3: The neighbor has sent 5 updates and received 3 updates.

The output shows Sent Updates: 5, Rcvd Updates: 3. So R1 sent 5 updates and received 3 updates, not the other way around.

A
The BGP session is in the 'Idle' state because the last read was 15 seconds ago.
Why wrong: The state is 'Established', not Idle. The last read time is normal for keepalive intervals.
B
The neighbor is an internal BGP peer because the remote AS is 65050.
Why wrong: The output says 'external link', so it is an eBGP peer. The remote AS being different from the local AS indicates eBGP.
C
The BGP session is up and functioning normally.
The state is Established, messages are being exchanged, and timers are within expected ranges.
D
The neighbor has sent 5 updates and received 3 updates.
Why wrong: The output shows Sent Updates: 5, Rcvd Updates: 3. So R1 sent 5 updates and received 3 updates, not the other way around.

Question 18hardmultiple choice

A network engineer runs the following command on Router R1:

R1# show bgp ipv4 unicast 10.0.0.0/8

BGP routing table entry for 10.0.0.0/8, version 25 Paths: (2 available, best #2, table default) Advertised to update-groups: 1 Refresh Epoch 1 65050 65100

10.0.1.2 from 10.0.1.2 (10.0.0.2)

Origin IGP, metric 0, localpref 100, weight 0, valid, external rx pathid: 0, tx pathid: 0x0 65050

10.0.1.3 from 10.0.1.3 (10.0.0.3)

Origin IGP, metric 0, localpref 100, weight 0, valid, external, best rx pathid: 0, tx pathid: 0x0

Based on this output, what can be concluded?

Trap 1: Path #1 is the best path because it has a longer AS_PATH,…

BGP prefers shorter AS_PATH, not longer.

Trap 2: Both paths are equally preferred, and BGP uses tie-breaking rules…

The paths are not equal because AS_PATH lengths differ.

Trap 3: Path #2 is the best path because it is received from a higher IP…

The best path selection is based on AS_PATH length, not neighbor IP address.

A
Path #1 is the best path because it has a longer AS_PATH, indicating more specific routing.
Why wrong: BGP prefers shorter AS_PATH, not longer.
B
Path #2 is the best path because it has a shorter AS_PATH.
Path #2 has AS_PATH length 1 (65050) while path #1 has length 2 (65050 65100). Shorter AS_PATH is preferred.
C
Both paths are equally preferred, and BGP uses tie-breaking rules like router ID.
Why wrong: The paths are not equal because AS_PATH lengths differ.
D
Path #2 is the best path because it is received from a higher IP address.
Why wrong: The best path selection is based on AS_PATH length, not neighbor IP address.

Question 19mediummultiple choice

router bgp 65000

bgp router-id 10.0.0.1

neighbor 10.0.0.2 remote-as 65001
 neighbor 10.0.0.2 route-map SET_COMMUNITY in

! route-map SET_COMMUNITY permit 10 set community 100:200 ! What is the effect of this configuration?

Trap 1: Routes received from 10.0.0.2 are tagged with community 100:200 and…

Incorrect. Communities are not sent by default; send-community is required.

Trap 2: The route-map is applied to outbound updates to 10.0.0.2, setting…

Incorrect. The 'in' keyword indicates the route-map is applied to inbound updates.

Trap 3: The configuration is invalid because the community must be a…

Incorrect. Numeric communities in the format AA:NN are valid.

A
Routes received from 10.0.0.2 are tagged with community 100:200, but the community is not sent to other BGP peers unless send-community is configured.
Correct. The route-map sets the community on inbound updates, but without send-community, the community is not propagated.
B
Routes received from 10.0.0.2 are tagged with community 100:200 and automatically sent to all neighbors.
Why wrong: Incorrect. Communities are not sent by default; send-community is required.
C
The route-map is applied to outbound updates to 10.0.0.2, setting community on routes sent to that neighbor.
Why wrong: Incorrect. The 'in' keyword indicates the route-map is applied to inbound updates.
D
The configuration is invalid because the community must be a string, not a numeric value.
Why wrong: Incorrect. Numeric communities in the format AA:NN are valid.

Question 20mediummultiple choice

router bgp 65000

bgp router-id 10.0.0.1

neighbor 10.0.0.2 remote-as 65000

! Which statement about this configuration is true?

Trap 1: This is an eBGP session because the neighbor IP is in a different…

Incorrect. eBGP requires a different AS number.

Trap 2: The router will automatically set next-hop-self for routes sent to…

Incorrect. next-hop-self is not enabled by default for iBGP.

Trap 3: The configuration is invalid because iBGP requires a loopback…

Incorrect. iBGP can use any interface; loopback is common but not required.

A
This is an iBGP session because the remote AS matches the local AS.
Correct. When remote-as equals the local AS, it is iBGP.
B
This is an eBGP session because the neighbor IP is in a different subnet.
Why wrong: Incorrect. eBGP requires a different AS number.
C
The router will automatically set next-hop-self for routes sent to this neighbor.
Why wrong: Incorrect. next-hop-self is not enabled by default for iBGP.
D
The configuration is invalid because iBGP requires a loopback interface.
Why wrong: Incorrect. iBGP can use any interface; loopback is common but not required.