350-401 · topic practice
Practise ENCOR 350-401 Bgp practice questions — original exam-style scenarios with answer choices, explanations, and analysis of common mistakes.
Courseiva uses original exam-style practice questions designed for learning and revision. The goal is to understand the concepts, recognise exam patterns, and improve through explanations — not memorise copied exam dumps.
What the exam tests
BGP questions usually test path selection attributes (AS-PATH, LOCAL_PREF, MED), eBGP vs iBGP rules, and why a route may be received but not used.
Watch out for
Practice set
20 questions · select your answer, then reveal the explanation
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Device hostname, vendor, model, OS version, serial number
Interface name, description, IP address, status, speed
BGP neighbor IP, remote AS, state, uptime
LLDP neighbor device ID, port ID, platform
Power supply, fan, temperature status
Drag steps to the numbered slots on the right, or tap a step then tap a slot.
Drag steps to the numbered slots on the right, or tap a step then tap a slot.
Trap 1: Increase the MTU on the link between the PE routers.
MTU issues would cause packet drops, not route absence.
Trap 2: Reconfigure LDP on the PE routers to establish a targeted session.
LDP is not directly related to VRF route import.
Trap 3: Check the MPLS label stack on the local PE to ensure labels are…
Label issues would affect all destinations, not just one.
Increase the MTU on the link between the PE routers.
Why wrong: MTU issues would cause packet drops, not route absence.
Reconfigure LDP on the PE routers to establish a targeted session.
Why wrong: LDP is not directly related to VRF route import.
Check the MPLS label stack on the local PE to ensure labels are being swapped correctly.
Why wrong: Label issues would affect all destinations, not just one.
Verify that the route target import/export values on the remote PE match those on the local PE for VRF CUSTOMER_C.
Correct: Mismatched route targets cause routes to not be imported into the VRF.
Trap 1: Weight
Incorrect. Weight is preferred with the highest value, not the lowest.
Trap 2: Local Preference
Incorrect. Local preference is preferred with the highest value.
Trap 3: AS Path Length
Incorrect. AS path length is preferred with the shortest length (lowest number of ASes), but it is not a single value attribute like MED.
Weight
Why wrong: Incorrect. Weight is preferred with the highest value, not the lowest.
Local Preference
Why wrong: Incorrect. Local preference is preferred with the highest value.
MED (Multi-Exit Discriminator)
Correct. MED is a metric that is preferred with the lowest value.
AS Path Length
Why wrong: Incorrect. AS path length is preferred with the shortest length (lowest number of ASes), but it is not a single value attribute like MED.
Trap 1: The AS-path contains the local AS number.
This is incorrect. While an AS-path containing the local AS number can cause routes to be rejected due to loop prevention, the typical symptom is routes not being received at all or being marked as invalid, not the specific 'received but not valid' status. The most common cause for 'not valid' is next-hop unreachability.
Trap 2: BGP synchronization is enabled.
This is incorrect. BGP synchronization is a legacy feature that requires the route to be in the IGP before it is advertised. In modern networks, synchronization is disabled by default. Even if enabled, it affects advertisement, not the validity of received routes in the BGP table.
Trap 3: The maximum-prefix limit has been exceeded.
This is incorrect. Exceeding the maximum-prefix limit typically causes the BGP session to reset or routes to be withdrawn, not to be marked as 'not valid' in the BGP table. Routes would likely be removed entirely, not just marked invalid.
The AS-path contains the local AS number.
Why wrong: This is incorrect. While an AS-path containing the local AS number can cause routes to be rejected due to loop prevention, the typical symptom is routes not being received at all or being marked as invalid, not the specific 'received but not valid' status. The most common cause for 'not valid' is next-hop unreachability.
The next-hop IP address is not reachable.
Correct. For a BGP route to be considered valid and installed in the routing table, the next-hop IP address must be reachable via an IGP or static route. If the next hop is not reachable, the route will appear in the 'show ip bgp' output but be marked as not valid.
BGP synchronization is enabled.
Why wrong: This is incorrect. BGP synchronization is a legacy feature that requires the route to be in the IGP before it is advertised. In modern networks, synchronization is disabled by default. Even if enabled, it affects advertisement, not the validity of received routes in the BGP table.
The maximum-prefix limit has been exceeded.
Why wrong: This is incorrect. Exceeding the maximum-prefix limit typically causes the BGP session to reset or routes to be withdrawn, not to be marked as 'not valid' in the BGP table. Routes would likely be removed entirely, not just marked invalid.
Consider the following configuration snippet:
router bgp 65000
bgp router-id 192.168.1.1
neighbor 10.0.0.2 remote-as 65001 neighbor 10.0.0.2 timers 10 30
!
What is the effect of the 'timers 10 30' command under the BGP neighbor?
Trap 1: It sets the keepalive interval to 10 seconds and the hold time to…
Incorrect. This command is under the neighbor context and affects only that specific neighbor.
Trap 2: It sets the BGP keepalive interval to 30 seconds and the hold time…
Incorrect. The first value is keepalive, second is hold time.
Trap 3: It configures the BGP session to use a keepalive of 10 seconds and…
Incorrect. The timers are configured locally; the neighbor must have matching or compatible timers to form the session.
It sets the keepalive interval to 10 seconds and the hold time to 30 seconds for all BGP neighbors.
Why wrong: Incorrect. This command is under the neighbor context and affects only that specific neighbor.
It sets the keepalive interval to 10 seconds and the hold time to 30 seconds for neighbor 10.0.0.2 only.
Correct. The timers command under a neighbor applies only to that neighbor.
It sets the BGP keepalive interval to 30 seconds and the hold time to 10 seconds for neighbor 10.0.0.2.
Why wrong: Incorrect. The first value is keepalive, second is hold time.
It configures the BGP session to use a keepalive of 10 seconds and a hold time of 30 seconds, but only if the neighbor supports it.
Why wrong: Incorrect. The timers are configured locally; the neighbor must have matching or compatible timers to form the session.
router bgp 65000
bgp router-id 10.0.0.1
neighbor 10.0.0.2 remote-as 65001 neighbor 10.0.0.2 ebgp-multihop 2 neighbor 10.0.0.2 update-source Loopback0
! What is the purpose of the ebgp-multihop 2 command?
Trap 1: It sets the maximum number of prefixes that can be received from…
Incorrect. That is controlled by maximum-prefix command.
Trap 2: It limits the number of paths BGP can install for load balancing to…
Incorrect. That is controlled by maximum-paths command.
Trap 3: It enables BGP multipath for eBGP with a hop count of 2.
Incorrect. ebgp-multihop does not enable multipath.
It allows the eBGP session to be established with a neighbor that is not directly connected, with a maximum of 2 hops.
Correct. ebgp-multihop increases the TTL to allow multi-hop eBGP.
It sets the maximum number of prefixes that can be received from the neighbor to 2.
Why wrong: Incorrect. That is controlled by maximum-prefix command.
It limits the number of paths BGP can install for load balancing to 2.
Why wrong: Incorrect. That is controlled by maximum-paths command.
It enables BGP multipath for eBGP with a hop count of 2.
Why wrong: Incorrect. ebgp-multihop does not enable multipath.
Drag steps to the numbered slots on the right, or tap a step then tap a slot.
Refer to the exhibit. ! NVE configuration interface nve1 no shut source-interface Loopback0 member vni 10100 mcast-group 239.1.1.100 ! ! VRF configuration vrf context TENANT-A rd 65000:1 address-family ipv4 unicast route-target both 65000:100 exit-address-family ! ! BGP EVPN configuration router bgp 65000 neighbor 10.1.1.1 remote-as 65000 neighbor 10.1.1.1 update-source Loopback0 address-family l2vpn evpn neighbor 10.1.1.1 activate neighbor 10.1.1.1 send-community extended ! ! VLAN configuration vlan 100 vn-segment 10100 ! ! Interface configuration interface Vlan100 no shutdown vrf member TENANT-A ip address 192.168.100.1/24
Trap 1: Remove the mcast-group from the NVE member, because EVPN uses BGP…
mcast-group is for data plane, but EVPN still needs the VNI enabled under evpn.
Trap 2: Change the source-interface to a physical interface.
Loopback is recommended for stability.
Trap 3: Add an IP address to the VLAN 100 interface in the default VRF.
The VLAN interface is correctly in VRF.
Configure "evpn" and "vni 10100 l2" under the BGP address-family l2vpn evpn.
The VNI must be activated under evpn for route advertisement.
Remove the mcast-group from the NVE member, because EVPN uses BGP for control plane.
Why wrong: mcast-group is for data plane, but EVPN still needs the VNI enabled under evpn.
Change the source-interface to a physical interface.
Why wrong: Loopback is recommended for stability.
Add an IP address to the VLAN 100 interface in the default VRF.
Why wrong: The VLAN interface is correctly in VRF.
Given the following SD-WAN configuration on a Cisco IOS-XE router:
router ospf 1
redistribute bgp 65000 subnets
network 192.168.1.0 0.0.0.255 area 0
!
interface GigabitEthernet0/0/0 ip address 192.168.1.1 255.255.255.0 ip ospf network point-to-point
!
Which statement is true?
Trap 1: The OSPF network type is point-to-point, so the dead interval…
The default dead interval for point-to-point is 40 seconds (4x hello of 10 seconds), not 120 seconds.
Trap 2: The redistribution of BGP into OSPF will cause OSPF to advertise…
Redistribution of BGP into OSPF will redistribute BGP routes, but OSPF will only advertise routes that match the network statement or are redistributed. However, the statement is too broad and may not be accurate for all BGP routes; also, SD-WAN overlay routes are typically in a separate VRF.
Trap 3: The configuration is incomplete because OSPF requires a router-id…
OSPF can automatically select a router-id from the highest loopback or physical interface IP. Manual configuration is not required.
The OSPF network type is point-to-point, so the hello interval defaults to 10 seconds on this interface.
On a point-to-point network type, the default OSPF hello interval is 10 seconds (same as broadcast). This is correct.
The OSPF network type is point-to-point, so the dead interval defaults to 120 seconds.
Why wrong: The default dead interval for point-to-point is 40 seconds (4x hello of 10 seconds), not 120 seconds.
The redistribution of BGP into OSPF will cause OSPF to advertise all BGP routes, including those learned via SD-WAN overlay.
Why wrong: Redistribution of BGP into OSPF will redistribute BGP routes, but OSPF will only advertise routes that match the network statement or are redistributed. However, the statement is too broad and may not be accurate for all BGP routes; also, SD-WAN overlay routes are typically in a separate VRF.
The configuration is incomplete because OSPF requires a router-id to be manually configured.
Why wrong: OSPF can automatically select a router-id from the highest loopback or physical interface IP. Manual configuration is not required.
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.
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.
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.
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.
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.
Trap 1: Set a lower MED for routes advertised to ISP A and a higher MED for…
Incorrect. MED is used to influence inbound traffic, but it is a multi-exit discriminator that is only considered when the same AS receives routes from multiple points. In a dual-homed scenario with different ISPs, MED is not typically used because the ISPs are different ASes.
Trap 2: Advertise a more specific prefix (e.g., /25) to ISP A and a less…
Incorrect. Advertising different prefix lengths can cause suboptimal routing and may not be accepted by ISPs. It is not a standard practice for load balancing.
Trap 3: Configure the CE router to use BGP multipath with both ISPs.
Incorrect. BGP multipath allows load balancing of outbound traffic, but it does not influence inbound traffic. The scenario requires different behaviors for inbound and outbound.
Set a lower MED for routes advertised to ISP A and a higher MED for routes advertised to ISP B.
Why wrong: Incorrect. MED is used to influence inbound traffic, but it is a multi-exit discriminator that is only considered when the same AS receives routes from multiple points. In a dual-homed scenario with different ISPs, MED is not typically used because the ISPs are different ASes.
Use AS path prepending on routes advertised to ISP B and set a higher local preference for routes learned from ISP A.
Correct. AS path prepending makes the path to ISP B longer, discouraging inbound traffic from using it. Setting a higher local preference for routes from ISP A makes outbound traffic prefer ISP A.
Advertise a more specific prefix (e.g., /25) to ISP A and a less specific prefix (/24) to ISP B.
Why wrong: Incorrect. Advertising different prefix lengths can cause suboptimal routing and may not be accepted by ISPs. It is not a standard practice for load balancing.
Configure the CE router to use BGP multipath with both ISPs.
Why wrong: Incorrect. BGP multipath allows load balancing of outbound traffic, but it does not influence inbound traffic. The scenario requires different behaviors for inbound and outbound.
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Carries IPv4 VPN routes with MPLS labels across the provider core
Carries IPv6 VPN routes with MPLS labels across the provider core
Carries global IPv4 unicast routes (non-VPN)
Carries global IPv6 unicast routes (non-VPN)
Carries Layer 2 VPN information such as pseudowires and VPLS
A network engineer issues the following command on Router R3:
R3# show ip bgp summary
BGP router identifier 10.0.0.3, local AS number 65003 BGP table version is 12345, main routing table version 12345
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.168.1.1 4 65001 12345 12345 12345 0 0 1w2d 150 192.168.1.2 4 65002 12345 12345 12345 0 0 2w0d 200
Based on this output, what can be concluded?
Trap 1: Both BGP neighbors are in the 'Idle' state.
The State/PfxRcd column shows numbers (150, 200), which means the session is established and prefixes are received.
Trap 2: The BGP session with 192.168.1.1 is down.
The presence of 150 prefixes indicates the session is up.
Trap 3: Router R3 is in AS 65001.
The local AS number is 65003, not 65001.
Both BGP neighbors are in the 'Idle' state.
Why wrong: The State/PfxRcd column shows numbers (150, 200), which means the session is established and prefixes are received.
Router R3 has received a total of 350 prefixes from its BGP neighbors.
150 + 200 = 350 prefixes received.
The BGP session with 192.168.1.1 is down.
Why wrong: The presence of 150 prefixes indicates the session is up.
Router R3 is in AS 65001.
Why wrong: The local AS number is 65003, not 65001.
Drag steps to the numbered slots on the right, or tap a step then tap a slot.
Trap 1: A route reflector client must be fully meshed with all other…
Incorrect: Route reflector clients do not need to be fully meshed; they only peer with the route reflector.
Trap 2: The route reflector modifies the AS_PATH attribute to prevent loops.
Incorrect: Route reflectors do not modify AS_PATH; they use the CLUSTER_LIST and ORIGINATOR_ID attributes for loop prevention.
Route reflectors allow iBGP speakers to advertise routes learned from other iBGP speakers without requiring a full mesh.
Correct: This is the primary purpose of route reflectors; they relax the full mesh requirement.
A route reflector client must be fully meshed with all other clients in the same cluster.
Why wrong: Incorrect: Route reflector clients do not need to be fully meshed; they only peer with the route reflector.
The route reflector can be a client of another route reflector.
Correct: Route reflectors can be hierarchical; a route reflector can be a client of another route reflector in a different cluster.
The cluster ID is used to prevent routing loops in a route reflector environment.
Correct: The cluster ID is added to the CLUSTER_LIST attribute to detect and prevent loops.
The route reflector modifies the AS_PATH attribute to prevent loops.
Why wrong: Incorrect: Route reflectors do not modify AS_PATH; they use the CLUSTER_LIST and ORIGINATOR_ID attributes for loop prevention.
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Well-known mandatory
Well-known discretionary
Optional transitive
Optional non-transitive
Well-known mandatory
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Highest
Highest
Lowest
Lowest
Lowest
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Establishes a BGP session and negotiates capabilities
Advertises new routes or withdraws previously advertised routes
Reports an error condition and closes the BGP session
Periodically sent to keep the BGP session alive
Requests that a peer readvertise its routes
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