Practise routing and connectivity troubleshooting scenarios involving R1, R2, R3, static routes, OSPF, next hops and routing tables.
Start Scenario PracticeDrag and drop the steps of OSPF summarization at ABR configuration steps into the correct order, from first to last.
Explanation: First, identify the subnets to summarize into a single prefix. Then, configure the area range command on the ABR under the OSPF process, specifying the area and the summary prefix. Optionally, set the 'not-advertise' keyword to suppress the summary. Verify the summary route in the OSPF database using 'show ip ospf summary-address'. Finally, check that the summary route appears in the routing table of other routers.
Drag and drop the steps of DHCP snooping operation on a Cisco switch into the correct order, from first to last.
Explanation: DHCP snooping begins by enabling the feature globally with 'ip dhcp snooping'. Then, the feature is enabled on specific VLANs. Trusted interfaces (typically uplinks to DHCP servers) are configured with 'ip dhcp snooping trust'. The switch then intercepts DHCP messages, building the DHCP snooping binding database from valid server responses. Finally, any DHCP server messages received on untrusted interfaces are dropped to prevent rogue server attacks.
A network engineer runs the following command on Switch SW1: SW1# show etherchannel summary Flags: D - down P - bundled in port-channel I - stand-alone s - suspended H - Hot-standby (LACP only) R - Layer3 S - Layer2 U - in use N - not in use, no aggregation f - failed to allocate aggregator M - not in use, minimum links not met u - unsuitable for bundling w - waiting to be aggregated d - default port Number of channel-groups in use: 1 Number of aggregators: 1 Group Port-channel Protocol Ports ------+-------------+-----------+-------------------------------------------- 1 Po1(SU) LACP Gi0/1(P) Gi0/2(P) Gi0/3(D) Based on this output, what can be concluded?
Explanation: The output shows that Gi0/1 and Gi0/2 have a flag of 'P' (bundled in port-channel), while Gi0/3 has a flag of 'D' (down). Therefore, only two ports are actively bundled, making option D correct. The 'SU' flags on Po1 indicate the port-channel is Layer 2 (S) and in use (U), not Layer 3.
A network engineer is configuring MPLS L3VPN on a Cisco IOS-XE router. The VRF CUSTOMER_C has route-target import 300:1 and export 300:1. The PE receives VPNv4 routes from the route reflector, but the CE router connected to the PE cannot ping any remote site IP addresses. The PE can ping the remote site IP addresses from the VRF. What is the most likely cause?
Explanation: The PE can ping remote site IP addresses from within the VRF, confirming that the VRF has the correct route-target import/export configuration and that VPNv4 routes are being received and installed in the VRF routing table. However, the CE router cannot ping remote sites, which indicates that the CE does not have a route pointing to the PE’s VRF interface as its next hop. Without a default route or a specific route pointing to the PE’s VRF-facing interface, the CE has no path to forward traffic to remote VPN destinations, even though the PE can reach them.
A network administrator is troubleshooting a BGP routing issue where routes from an eBGP neighbor are not being installed in the routing table. The 'show ip bgp' output shows the routes are received but not valid. What is the most likely cause?
Explanation: 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 a static route. If the next hop is not reachable, the route will appear in the 'show ip bgp' output but will be marked as not valid (often with a 'r' for received but not valid). This is the most common cause when routes are received from an eBGP neighbor but not installed.
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Practice all Router R1 Cannot Reach R3 Practice QuestionsPractise routing and connectivity troubleshooting scenarios involving R1, R2, R3, static routes, OSPF, next hops and routing tables. These appear throughout the 350-401 and require you to apply your knowledge, not just recall facts.
Cisco doesn't publish an exact breakdown, but scenario-based questions (especially exhibit and command-output formats) make up a significant portion of the 350-401. Practicing each scenario type ensures you're ready for any format.
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