300-410 Practice Test 34 — 15 Questions

Question 1

An engineer configures BFD on an OSPF link and also applies a distribute-list outbound under the OSPF process. The BFD session is up, but OSPF routes are not being advertised to the neighbor. The engineer verifies that the distribute-list is correctly configured. What is the most likely cause?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

The 'area range' command is configured on the ABR, summarizing the route, and the distribute-list is filtering the summary.. OSPF distribute-list outbound only filters routes that are being redistributed into OSPF, not intra-area or inter-area LSAs. On an ABR, the 'area range' command generates a summary LSA (type 3), which can be filtered by a distribute-list outbound if it references that specific summary route. In this scenario, the distribute-list is correctly configured to deny the network, and the ABR summarizes that network via 'area range', causing the summary LSA to be filtered and not advertised to the neighbor. BFD does not affect this behavior.

Answer

The distribute-list is applied outbound, but OSPF distribute-lists only filter routes in the routing table, not LSAs, so the routes are still advertised.

Answer

The BFD session is flapping due to a mismatch in the 'bfd interval' command, causing OSPF to withdraw routes.

Answer

The distribute-list references an ACL that denies the network, but OSPF uses type 3 LSAs that are not affected by ACLs.

Question 2

A network engineer runs the following command to troubleshoot an ERSPAN issue:

R1# show monitor session 6 detail
Session 6
---------
Type                   : ERSPAN Source Session
Source VLANs           : 
    Both               : 10-20
Destination IP         : 10.1.1.3
ERSPAN ID              : 200

What does this output indicate?

Accepted Answer

The session is correctly configured to monitor VLANs 10 through 20.. The output shows an ERSPAN source session with source VLANs 10-20, destination IP 10.1.1.3, and ERSPAN ID 200. This is a valid ERSPAN source session using VLANs as the source.

Answer

The session is misconfigured because ERSPAN cannot use VLANs as source.

Answer

The session is misconfigured because the ERSPAN ID must be less than 100.

Answer

The session is misconfigured because the destination IP must be on the same subnet.

Question 3

A DMVPN Phase 3 network with EIGRP as the routing protocol experiences intermittent connectivity between spokes. R1 (hub) has 'ip summary-address eigrp 100 10.0.0.0 255.255.0.0' configured on the tunnel interface. R2 (spoke) shows 'show ip eigrp topology all-links' listing 10.1.0.0/24 as reachable via R1, but traffic from R2 to 10.1.0.1 (another spoke) is forwarded to R1 instead of directly via the spoke-to-spoke tunnel. What is the root cause?

Accepted Answer

The summary route on the hub creates a less specific route that is preferred over the more specific /24 routes learned from other spokes, causing suboptimal routing.. The hub's summary route 10.0.0.0/16 is advertised to spokes, causing them to prefer the summary route over the more specific /24 routes learned from other spokes via NHRP redirect. This prevents spoke-to-spoke direct tunnels from being established or used, as traffic is forwarded to the hub based on the summary route.

Answer

EIGRP stub configuration on spokes prevents them from learning routes from other spokes.

Answer

NHRP redirect is disabled on the hub, preventing spoke-to-spoke tunnel establishment.

Answer

The spoke-to-spoke tunnel interface has a different MTU causing fragmentation.

Question 4

What is the maximum hop count for a route in RIP?

Accepted Answer

15. RIP (Routing Information Protocol) uses a maximum hop count of 15 to prevent routing loops. A route with a hop count of 16 is considered unreachable (infinite metric). This limit is defined in RFC 1058 for RIPv1 and RFC 2453 for RIPv2, ensuring that the network diameter remains small and loop-free.

Answer

16

Answer

255

Answer

32

Question 5

An engineer configures mutual redistribution between OSPF and EIGRP on a router. After configuration, routing loops occur. Which is the most likely explanation?

Accepted Answer

The administrative distance of the redistributed routes is not modified, causing the redistributed route to be preferred over the original.. Mutual redistribution without route tagging or filtering can cause routing loops. When a route redistributed from OSPF into EIGRP is then redistributed back into OSPF, it can be preferred over the original route if the administrative distance is lower, creating a loop. This is a classic edge case that requires careful use of route tags and distribute-lists.

Answer

The seed metric is not configured for EIGRP redistribution.

Answer

The OSPF process ID is mismatched.

Answer

The redistribute command is missing the subnets keyword.

Question 6

A network engineer runs the following command on Router R1:

R1# show ip eigrp interfaces detail GigabitEthernet0/0

IP-EIGRP interfaces for process 100

Interface                    Peers  Xmit Queue   Mean   Pacing Time   Multicast    Pending
                              Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Gi0/0                          1       0/0       10       0/10          50           0
  Hello interval: 5 sec, Hold time: 15 sec
  Split horizon is enabled
  Summary address: 10.0.0.0/8
  Next xmit serial <none>
  Un/reliable mcasts: 0/0  Un/reliable ucasts: 0/0
  Mcast exceptions: 0  CR packets: 0  ACKs suppressed: 0
  Retransmissions: 0  Retry timer: 15
  Hello packets sent: 100, received: 99

Based on this output, what is the purpose of the summary address configured on this interface?

Accepted Answer

It advertises a summary route 10.0.0.0/8 to neighbors.. The 'Summary address: 10.0.0.0/8' line shows that a manual summary route is configured on this interface, which will be advertised to EIGRP neighbors.

Answer

It filters all routes in the 10.0.0.0/8 range.

Answer

It redistributes connected routes.

Answer

It disables split horizon.

Question 7

Which TWO commands can be used to verify the operation of IPv6 First Hop Security features such as RA Guard and DHCPv6 Guard on a Cisco IOS-XE switch? (Choose TWO.)

Accepted Answer

show ipv6 snooping. The 'show ipv6 snooping' command is the primary verification tool for IPv6 First Hop Security (FHS) features, including RA Guard and DHCPv6 Guard. It displays the IPv6 snooping policy database, which tracks all discovered IPv6 neighbors and their binding states, directly reflecting the operational status of RA Guard and DHCPv6 Guard enforcement on the switch.

Answer

show ipv6 nd raguard

Answer

show ipv6 dhcp binding

Answer

show ipv6 source guard

Question 8

A network engineer is troubleshooting an IPsec site-to-site VPN that uses a GRE tunnel. The GRE tunnel is up/up, and EIGRP is forming an adjacency over it. However, traffic from the local LAN to the remote LAN is not working. The engineer pings the remote LAN IP from the local router and it succeeds. What is the most likely cause?

Accepted Answer

The local router does not have a route to the remote LAN subnet in its routing table.. The GRE tunnel and routing protocol are working, but traffic from the LAN is failing. This indicates that the routing table on the local router does not have a route to the remote LAN subnet, or the route points to the wrong next-hop. The ping from the router succeeds because the router uses its own IP as source, which is directly connected to the tunnel.

Answer

The crypto map access list does not include the local LAN subnet.

Answer

The GRE tunnel keepalive is disabled.

Answer

The IPsec transform set is missing authentication.

Question 9

An enterprise uses EIGRP for IPv6 with route summarization. Router R1 has a summary route 2001:db8:1::/48 via Null0 redistributed into EIGRP. Router R2 receives this summary and has a more specific route 2001:db8:1:1::/64 learned via a different interface. R2's IPv6 uRPF is configured in strict mode on the interface facing R1. Traffic from a host behind R2 destined to 2001:db8:1:2::1 is being dropped. R2 shows 'ipv6 cef' indicates the summary route points to R1, but uRPF checks fail. What is the root cause?

Accepted Answer

The summary route 2001:db8:1::/48 on R1 causes R2 to have a less specific route pointing to R1, making uRPF think the source address is not reachable via the incoming interface.. R2's strict mode uRPF checks that the source address of incoming traffic is reachable via the exact interface on which the packet arrived. When R2 receives a packet from a host behind it destined to 2001:db8:1:2::1, the source address is from the host's subnet (e.g., 2001:db8:1:2::/64). R2's FIB has a less specific summary route 2001:db8:1::/48 pointing to R1 (via the interface facing R1), but the more specific /64 route is learned via a different interface. Strict uRPF requires a matching route in the FIB that points back out the same interface the packet arrived on; since the summary route points to R1's interface, uRPF fails, dropping the traffic.

Answer

R2's uRPF is configured in loose mode, which requires a matching route in the FIB, but the summary route is not installed.

Answer

EIGRP redistribution of the summary route creates a routing loop, causing uRPF to fail.

Answer

The host behind R2 has an incorrect source address, causing uRPF to drop all traffic.

Question 10

A network engineer runs the following command on Router R1:

R1# show ip eigrp topology
EIGRP-IPv4 Topology Table for AS(100)/ID(192.168.1.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
       r - reply Status, s - sia Status

P 10.10.10.0/24, 1 successors, FD is 28160
         via 10.1.1.2 (28160/28160), GigabitEthernet0/0
P 10.20.20.0/24, 1 successors, FD is 28160
         via 10.2.2.2 (28160/28160), GigabitEthernet0/1
P 10.30.30.0/24, 1 successors, FD is 28160
         via 10.3.3.2 (28160/28160), GigabitEthernet0/2
A 10.40.40.0/24, 0 successors, FD is Infinity
         via 10.4.4.2 (Infinity/Infinity), GigabitEthernet0/3

Based on this output, what is the problem?

Accepted Answer

The route to 10.40.40.0/24 is stuck-in-active and may cause a network instability.. The route to 10.40.40.0/24 is in the Active (A) state with 0 successors and an FD of Infinity, meaning the router has lost its only feasible successor and is actively querying neighbors for a new path. This is a stuck-in-active (SIA) condition because the neighbor 10.4.4.2 is not replying, causing the route to remain active indefinitely and potentially destabilizing the EIGRP domain.

Answer

The route to 10.40.40.0/24 is passive and stable.

Answer

The route to 10.30.30.0/24 has a feasible successor.

Answer

All routes are in a stable passive state.

Question 11

Which THREE statements about BFD multihop sessions are true? (Choose THREE.)

Accepted Answer

Multihop BFD is used when the neighbors are not directly connected.. BFD multihop sessions are used when the two routers are not directly connected, requiring multiple hops. They use a different destination UDP port (4784) compared to single-hop sessions (3784). Additionally, multihop sessions require explicit configuration of the BFD source and destination IP addresses. The other statements are false because multihop sessions do not require the same subnet, and they can operate over any routed path.

Answer

Multihop BFD requires both routers to be in the same subnet.

Answer

Multihop BFD can only be used with BGP.

Question 12

A network engineer runs the following command on Router R1:

R1# show ip access-lists
Extended IP access list 170
    10 permit icmp any any echo (100 matches)
    20 permit icmp any any echo-reply (80 matches)
    30 deny ip any any (10 matches)

Based on this output, which statement is correct?

Accepted Answer

Only ICMP echo and echo-reply are permitted; all other IP traffic is denied.. The ACL 170 explicitly permits only ICMP echo (type 8) and echo-reply (type 0) traffic, as shown by the match counters. The final deny ip any any statement blocks all other IP traffic, including other ICMP types and non-ICMP IP protocols. Therefore, only ICMP echo and echo-reply are permitted; all other IP traffic is denied, making option B correct.

Answer

All ICMP traffic is permitted.

Answer

The ACL permits all IP traffic.

Answer

The ACL is not applied.

Question 13

A network engineer is troubleshooting a scenario where a router is dropping IPv6 packets that are destined for a server on a directly connected network. The engineer checks the interface and finds that uRPF is enabled in loose mode. The router has a default route pointing to an upstream router. The source address of the packets is 2001:db8:100::1, which is not in the routing table (the router has no route to that prefix). What is the most likely cause of the packet drops?

Accepted Answer

The uRPF loose mode check fails because there is no route to the source address in the routing table.. With uRPF loose mode enabled, the router checks whether a route to the source address exists in the routing table, but it does not verify that the incoming interface matches the reverse path. Since the source address 2001:db8:100::1 is not present in the routing table, the loose mode check fails and the packets are dropped. The presence of a default route does not help because uRPF requires an exact match for the source prefix, not a default route.

Answer

The uRPF loose mode check fails because the source address is not reachable via the same interface.

Answer

The router has an ACL that blocks traffic from that source.

Answer

The uRPF mode should be strict mode to allow the traffic.

Question 14

A network engineer runs the following command on Router R1:

R1# show ip interface GigabitEthernet0/1
GigabitEthernet0/1 is up, line protocol is up
  Internet address is 10.1.1.1/24
  Broadcast address is 255.255.255.255
  Address determined by non-volatile memory
  MTU is 1500 bytes
  Helper address is not set
  Directed broadcast forwarding is disabled
  Outgoing access list is 101
  Inbound access list is not set

Based on this output, which statement is correct?

Accepted Answer

ACL 101 filters traffic leaving the interface.. The command output shows 'Outgoing access list is 101', which indicates that ACL 101 is applied to filter traffic leaving the GigabitEthernet0/1 interface. This is confirmed by the absence of an 'Inbound access list' entry, meaning no ACL is applied to incoming traffic. Therefore, ACL 101 filters traffic leaving the interface.

Answer

ACL 101 filters traffic entering the interface.

Answer

The interface has no ACL applied.

Answer

ACL 101 is applied in both directions.

Question 15

A network engineer runs the following command to debug IPv6 uRPF with detailed information:

R1# debug ipv6 verify detail
IPv6 verify debugging is on (detail)

*Mar 1 00:03:45.678: IPv6 verify: source 2001:DB8:5::1 on GigabitEthernet0/0
*Mar 1 00:03:45.678:   route to source via GigabitEthernet0/1, not same as input interface

What does this output indicate?

Accepted Answer

The packet will be dropped because strict uRPF requires the return path to be through the same interface.. The debug output shows that the source address 2001:DB8:5::1 is reachable via GigabitEthernet0/1, but the packet arrived on GigabitEthernet0/0. With strict unicast Reverse Path Forwarding (uRPF), the router verifies that the best return route to the source uses the same interface on which the packet was received. Since the interfaces do not match, the router drops the packet to prevent spoofing.

Answer

The packet will be forwarded because a route exists.

Answer

The packet will be forwarded because uRPF is loose.

Answer

The router will change the route to use GigabitEthernet0/0.