300-410 Practice Test 31 — 15 Questions

Question 1

Router R3 has the following configuration:
```
interface GigabitEthernet0/4
 ip address 10.3.3.3 255.255.255.0
 ip policy route-map PBR-IN
!
route-map PBR-IN permit 10
 match ip address 102
 set ip next-hop verify-availability 192.168.2.1 10 track 1
!
access-list 102 permit ip 10.3.3.0 0.0.0.255 any
```
What is the effect of the 'set ip next-hop verify-availability' command?

Accepted Answer

The next-hop 192.168.2.1 is used only if track object 1 is up; otherwise, normal routing applies.. The command 'set ip next-hop verify-availability 192.168.2.1 10 track 1' in a route-map specifies that the next-hop 192.168.2.1 should be used only if the tracked object (track 1) is in the 'up' state. The number 10 is the sequence number for this next-hop entry, allowing multiple next-hops to be tried in order. If track 1 is down, the policy-based routing (PBR) action for that sequence is skipped, and the router falls back to the normal routing table to forward the packet. Thus, option A correctly describes this conditional behavior.

Answer

The next-hop 192.168.2.1 is always used regardless of track status.

Answer

The router pings 192.168.2.1 every 10 seconds to verify reachability.

Answer

The configuration is invalid because 'verify-availability' requires a sequence number.

Question 2

A network engineer runs the following command on Router R4:

R4# show logging | include %BGP-3-NOTIFICATION

*Mar  1 00:01:05.123: %BGP-3-NOTIFICATION: sent to neighbor 10.0.0.2 4/0 (Hold Timer Expired) 0 bytes
*Mar  1 00:02:10.456: %BGP-3-NOTIFICATION: received from neighbor 10.0.0.2 4/0 (Hold Timer Expired) 0 bytes
*Mar  1 00:03:15.789: %BGP-3-NOTIFICATION: sent to neighbor 10.0.0.2 4/0 (Hold Timer Expired) 0 bytes

Based on this output, what is the most likely problem?

Accepted Answer

There is a connectivity issue causing keepalive packets to be lost.. The log shows BGP NOTIFICATION messages with error code 4/0, which is 'Hold Timer Expired.' This means the router did not receive a KEEPALIVE or UPDATE from neighbor 10.0.0.2 within the negotiated hold time (typically 3× the keepalive interval, default 180 seconds). Since the neighbor is reachable enough to have formed the session initially, the most likely cause is intermittent connectivity or packet loss dropping the keepalives, not a configuration mismatch.

Answer

The BGP neighbor has a mismatched autonomous system number.

Answer

The BGP update interval is too short, causing excessive updates.

Answer

The router is configured with soft-reconfiguration inbound, causing memory issues.

Question 3

What is the default maximum number of paths that BGP can install in the routing table using the 'maximum-paths' command in Cisco IOS?

Accepted Answer

1. In Cisco IOS, the default maximum number of paths that BGP can install in the routing table when using the maximum-paths command is 1. This means that by default, BGP will only install the best path, and not perform equal-cost multipath (ECMP) unless configured otherwise.

Answer

2

Answer

4

Answer

6

Question 4

A network engineer is troubleshooting BGP route summarization on a border router that advertises a summary route 172.16.0.0/16 to an ISP neighbor. The engineer notices that the ISP is receiving the summary route but also receiving the more specific routes (172.16.1.0/24, 172.16.2.0/24), causing suboptimal routing. What should the engineer do to ensure only the summary route is advertised?

Accepted Answer

Use the 'aggregate-address 172.16.0.0 255.255.0.0 summary-only' command under the BGP process.. In BGP, to suppress more specific routes when advertising a summary, the engineer must use the 'aggregate-address' command with the 'summary-only' keyword.

Answer

Configure the 'network' command for the summary route and remove the network statements for the specific subnets.

Answer

Apply a route-map to the neighbor to filter out the specific routes using an ACL.

Answer

Configure the 'summary-address' command under the BGP process.

Question 5

Examine the following partial configuration on R1:

!--- R1 configuration
route-map RMAP permit 10
 match ip address prefix-list PL-1
 set metric 100
!
route-map RMAP permit 20
 set metric 200
!
router eigrp 100
 network 10.0.0.0
 redistribute ospf 1 metric 1000 100 255 1 1500 route-map RMAP
!

What is the effect of this configuration?

Accepted Answer

Routes matching prefix-list PL-1 are redistributed with metric 100; all other OSPF routes are redistributed with metric 200.. The route-map RMAP has two permit sequences. The first matches prefix-list PL-1 and sets metric to 100. The second is a catch-all permit with no match, setting metric to 200. All redistributed OSPF routes will match either sequence and have their metric set accordingly. If a route matches the first sequence, its metric is set to 100; otherwise, it matches the second and gets metric 200. There is no deny sequence, so no routes are filtered.

Answer

Only routes matching prefix-list PL-1 are redistributed into EIGRP with metric 100; all other OSPF routes are denied.

Answer

The route-map is missing a deny statement; without it, all routes are permitted with default metric.

Answer

The route-map is applied to redistribution, but the metric values are ignored because redistribute command also specifies metric.

Question 6

An engineer enables unicast RPF (uRPF) in strict mode on an interface. Afterward, some legitimate traffic from a BGP neighbor is dropped. The neighbor has two paths to the router, and traffic may arrive on a different interface than the return path. What is the most likely explanation?

Accepted Answer

Strict uRPF drops packets if the source IP is not reachable via the receiving interface, which fails in asymmetric routing scenarios.. Strict unicast RPF checks that the source IP of each incoming packet is reachable through the same interface on which the packet arrived, using the FIB. In an asymmetric routing scenario where the BGP neighbor has two paths and return traffic leaves via a different interface than the one receiving the packet, the reverse lookup fails and strict uRPF drops the legitimate traffic. This is the classic failure mode of strict mode in multihomed or load-balanced designs.

Answer

The uRPF 'allow-default' option was not configured, so default routes are ignored.

Answer

The neighbor's BGP updates have a source IP that is not in the routing table.

Answer

Loose mode should be used instead, but strict mode was configured by mistake.

Question 7

Which TWO statements about PBR and the 'set ip next-hop recursive' command are true? (Choose TWO.)

Accepted Answer

The 'set ip next-hop recursive' command can specify a next-hop address that is not directly connected, and the router will perform a recursive lookup to determine the outgoing interface.. The 'set ip next-hop recursive' command allows PBR to use a next-hop address that is not directly connected; the router performs recursive lookup to find the outgoing interface. This is different from 'set ip next-hop' which requires a directly connected next hop. The recursive option is useful when the next hop is multiple hops away. However, it can impact performance due to the recursive lookup.

Answer

The 'set ip next-hop recursive' command is the default behavior for 'set ip next-hop' when the next hop is not directly connected.

Answer

The 'set ip next-hop recursive' command is only supported on Cisco IOS-XE platforms, not on classic IOS.

Answer

When using 'set ip next-hop recursive', the router will drop the packet if the recursive lookup fails to find a route to the next hop.

Question 8

Which TWO statements about the interaction between administrative distance and floating static routes are true? (Choose TWO.)

Accepted Answer

A floating static route must have an administrative distance higher than the primary route's AD to serve as a backup.. Option A is correct because a floating static route is designed to stay out of the routing table while the primary route is active, so its administrative distance must be higher than the primary route's AD (for example, a static route with AD 200 backing up an OSPF route with AD 110). Option D is correct because the Cisco 'ip route' command accepts an optional administrative distance argument at the end of the syntax (e.g., 'ip route 192.168.2.0 255.255.255.0 10.1.1.2 200'), which is exactly how a floating static route is configured. Option B is incorrect because the default administrative distance for a static route is 1, not 0 (0 is used for directly connected interfaces). Option C is incorrect because a route is only installed if its next hop is resolvable/reachable; an unreachable next hop prevents installation. Option E is incorrect because floating static routes can back up any routing protocol (OSPF, EIGRP, RIP, BGP, etc.) or even another static route, not just OSPF.

Answer

The default administrative distance for a static route is 0.

Answer

A floating static route will be installed in the routing table immediately after the primary route is removed, even if the next-hop is unreachable.

Answer

A floating static route can only be used with OSPF as the primary routing protocol.

Question 9

Which statement correctly describes the behavior of IPv6 Unicast Reverse Path Forwarding (uRPF) in strict mode?

Accepted Answer

It verifies that the source address is reachable via the same interface and that the route points back to that interface.. IPv6 uRPF strict mode requires that the source address of an incoming packet is reachable via the exact same interface on which the packet arrived, and that the best matching route in the FIB points back to that interface. This prevents spoofed traffic by ensuring the source is topologically correct from the router's perspective, as defined in RFC 3704.

Answer

It verifies that the source address is in the routing table, but does not check the incoming interface.

Answer

It checks that the source address is reachable via the same interface and that the route is a connected route.

Answer

It only checks that the source address is not a multicast or link-local address.

Question 10

An engineer configures Flexible NetFlow with a user-defined flow record that includes 'match ipv4 source address' and 'collect counter bytes'. Which TWO additional statements about this configuration are true? (Choose TWO.)

Accepted Answer

The 'match ipv4 source address' command defines a key field that is used to uniquely identify flows.. In Flexible NetFlow, the 'match' fields define the flow key; flows are uniquely identified by the combination of all match fields. The 'collect' fields define non-key data that is aggregated per flow. The flow record must be referenced by a flow monitor, which is then applied to an interface. The default flow record is 'netflow-original', which includes many default keys. The 'match' fields cannot be omitted; at least one match field is required. The 'collect' fields are optional and can include counters, timestamps, etc.

Answer

The flow record must be applied directly to an interface using the 'ip flow record' command.

Answer

If no 'match' commands are configured, the router will use the default match fields from the 'netflow-original' record.

Answer

The flow record can be used by both IPv4 and IPv6 traffic simultaneously without additional configuration.

Question 11

A network engineer runs the following command to troubleshoot an MPLS L3VPN issue:

R1# show bgp neighbors 10.0.0.2 received-routes

Output:
BGP table version is 10, local router ID is 10.0.0.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S stale, m multipath, b backup-path, f RT-Filter,
x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete

Network          Next Hop            Metric LocPrf Weight Path
*> 10.3.3.0/24      10.0.0.2                 0    100      0 65000 i
*> 10.4.4.0/24      10.0.0.2                 0    100      0 65000 i

Total number of prefixes 2

What does this output indicate?

Accepted Answer

R1 is receiving two routes from BGP neighbor 10.0.0.2. The show bgp neighbors received-routes command displays routes received from the specified neighbor. Here, R1 has received two prefixes (10.3.3.0/24 and 10.4.4.0/24) from neighbor 10.0.0.2, with next hop 10.0.0.2 and AS path 65000. These are valid and best.

Answer

R1 is advertising two routes to BGP neighbor 10.0.0.2

Answer

R1 has no BGP routes

Answer

R1 is using OSPF to learn these prefixes

Question 12

A network engineer runs the following command to debug MPLS LDP session establishment:

R1# debug mpls ldp session

Output:
*Mar  1 00:01:23.456: LDP: Session with 10.0.0.2:0 (0x1234) is UP
*Mar  1 00:01:24.567: LDP: Session with 10.0.0.2:0 (0x1234) is DOWN
*Mar  1 00:01:25.678: LDP: Session with 10.0.0.2:0 (0x1234) is UP
*Mar  1 00:01:26.789: LDP: Session with 10.0.0.2:0 (0x1234) is DOWN

What does this output indicate?

Accepted Answer

The LDP session with 10.0.0.2 is flapping. The debug output shows the LDP session with neighbor 10.0.0.2 is flapping (repeatedly going UP and DOWN). This indicates instability in the LDP session.

Answer

The LDP session with 10.0.0.2 is stable

Answer

The LDP session with 10.0.0.2 is using targeted hello

Answer

The LDP session with 10.0.0.2 is down permanently

Question 13

A network engineer runs the following command to verify NAT translations:

R1# show ip nat translations verbose
Pro Inside global      Inside local       Outside local      Outside global
--- 10.2.2.2           10.1.1.1           192.168.1.1        192.168.1.1
  create 00:00:15, use 00:00:05, flags: extended, timing-out

What does the 'extended' flag indicate?

Accepted Answer

The translation includes port information, typical of PAT.. The 'extended' flag in the output of 'show ip nat translations verbose' indicates that the NAT translation includes Layer 4 port information, which is characteristic of Port Address Translation (PAT) or NAT overload. This allows multiple internal hosts to share a single public IP address by using unique port numbers, as opposed to a simple one-to-one translation without port multiplexing.

Answer

The translation is for a single port only.

Answer

The translation is static and never times out.

Answer

The translation is for a VPN tunnel.

Question 14

An engineer configures SPAN on a Cisco switch to monitor traffic from a VLAN, but the VLAN includes a voice VLAN. The mirrored traffic shows only data traffic, not voice. What is the most likely explanation?

Accepted Answer

The SPAN source is configured for the data VLAN only, not the voice VLAN.. Voice VLANs are often configured as separate VLANs (e.g., VLAN 100 for voice, VLAN 10 for data). If the SPAN source is a single VLAN, it only captures traffic on that VLAN. To capture both, the SPAN session must include both VLANs or use a port-based source that includes both.

Answer

Voice traffic uses a different CoS value, which SPAN ignores.

Answer

The voice VLAN is configured as a native VLAN, which SPAN does not capture.

Answer

The switch has a security ACL that blocks voice traffic from being mirrored.

Question 15

In an MPLS L3VPN environment using MP-BGP, what is the default value of the BGP keepalive timer on Cisco IOS-XE?

Accepted Answer

60 seconds. The default BGP keepalive timer is 60 seconds, as defined in RFC 4271 and implemented in Cisco IOS-XE.

Answer

30 seconds

Answer

90 seconds

Answer

180 seconds