300-410 Practice Test 14 — 15 Questions

Question 1

An engineer configures DHCPv6 prefix delegation on a router with multiple requesting interfaces. The router receives a /48 prefix from the server, but only one interface gets a /64 sub-prefix. Which is the most likely explanation?

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

Accepted Answer

Only one interface is configured with 'ipv6 address prefix-name ::1:0:0:0:1/64' using the delegated prefix; other interfaces lack this configuration.. The router receives a /48 prefix from the DHCPv6 server, but each requesting interface must explicitly reference the delegated prefix using the 'ipv6 address prefix-name' command to derive a /64 sub-prefix. If only one interface has this configuration, only that interface will obtain a /64 sub-prefix; the other interfaces lack the necessary command to consume the delegated prefix.

Answer

The DHCPv6 server only delegates a single /64 prefix, not a /48.

Answer

The router's 'ipv6 dhcp client pd' command is missing the 'rapid-commit' option.

Answer

The router has 'ipv6 dhcp client information refresh' set to a high value, delaying updates.

Question 2

An enterprise uses VRF-lite with IPv6. VRF A on R1 leaks routes to VRF B using route-target import/export. R1 has an IPv6 ACL applied inbound on the interface in VRF A that permits only OSPFv3 and denies all other traffic. R1's VRF B has a static default route pointing to a next-hop in VRF A. Traffic from VRF B to the internet fails. R1 shows 'ping vrf B 2001:db8:2::1' fails, but 'ping vrf A 2001:db8:2::1' succeeds. What is the root cause?

Accepted Answer

The ACL on the VRF A interface blocks data traffic from VRF B, which is forwarded via the leaked route.. The ACL on the VRF A interface is configured to permit only OSPFv3 (IPv6 routing protocol traffic) and deny all other traffic. When VRF B leaks routes to VRF A, data traffic from VRF B destined to the internet is forwarded via the leaked route and enters the VRF A interface. This data traffic is not OSPFv3, so it is denied by the ACL, causing the ping to fail. The ping from VRF A succeeds because it originates within VRF A and does not traverse the ACL inbound on the same interface.

Answer

Route leaking is not configured correctly; the route-target import/export is missing.

Answer

The static default route in VRF B has an incorrect next-hop address.

Answer

uRPF is enabled on the VRF A interface and drops traffic from VRF B due to source address mismatch.

Question 3

What is the default DHCPv6 client DUID type on a Cisco IOS-XE router?

Accepted Answer

DUID-LL (Link-Layer). Cisco IOS-XE routers default to DUID-LL (Link-Layer) as the DHCPv6 client DUID type, as defined in RFC 8415. This DUID is generated using the router's link-layer address (MAC address) without a timestamp, making it stable across reboots. The DUID-LL is the default because it provides a consistent identifier without requiring clock synchronization or enterprise registration.

Answer

DUID-LLT (Link-Layer plus Time)

Answer

DUID-EN (Enterprise Number)

Answer

DUID-UUID (Universally Unique Identifier)

Question 4

Consider the following EEM applet configuration:

!---
event manager applet CHECK_OSPF
event syslog pattern "OSPF-5-ADJCHG"
action 1.0 cli command "enable"
action 2.0 cli command "show ip ospf neighbor"
action 3.0 mail server "smtp.example.com" to "admin@example.com" from "router@example.com" subject "OSPF Adjacency Change" body "An OSPF adjacency change has been detected."
!---

What is the effect of this configuration?

Accepted Answer

The applet will send an email to the administrator whenever an OSPF adjacency change occurs.. The EEM applet triggers on a syslog message matching the pattern "OSPF-5-ADJCHG". When triggered, it sends an email notification to the administrator. The 'cli command' actions are executed but their output is not used; the email is sent regardless. The applet does not require any additional configuration to send the email, provided the mail server is reachable.

Answer

The applet will only execute the CLI commands and will not send an email because the mail server is not configured globally.

Answer

The applet will fail because the 'event syslog pattern' must be configured with a regular expression.

Answer

The applet will send the email only after the CLI commands complete, but the output of those commands is not included in the email.

Question 5

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

R1# debug event manager action cli

EEM Action CLI debugging is on

R1#
Mar  1 00:10:15.123: %HA_EM-6-ACTION: applet TRACK-INTERFACE: action cli command: 'show ip int brief' executed
Mar  1 00:10:15.456: %HA_EM-6-ACTION: applet TRACK-INTERFACE: action cli output: 'Interface                  IP-Address      OK? Method Status                Protocol
GigabitEthernet0/0         192.168.1.1     YES NVRAM  up                    up
GigabitEthernet0/1         10.0.0.1        YES NVRAM  up                    up
Loopback0                  1.1.1.1         YES NVRAM  up                    up'

What does this output indicate?

Accepted Answer

The EEM applet 'TRACK-INTERFACE' executed the command 'show ip int brief' and the output was displayed.. The debug output shows the execution of CLI actions within an EEM applet. It displays the applet name, the CLI command being executed, and the output of that command. This is useful for verifying that CLI actions are working correctly and seeing the exact output returned.

Answer

The EEM applet 'TRACK-INTERFACE' failed to execute the command 'show ip int brief'.

Answer

The debug output shows the EEM applet configuration for 'TRACK-INTERFACE'.

Answer

The command 'show ip int brief' was executed manually by the engineer.

Question 6

What is the default DHCPv4 renewal time (T1) as a percentage of the lease time?

Accepted Answer

50%. (50%) because RFC 2131 defines the DHCPv4 renewal time (T1) as 50% of the lease duration. When the T1 timer expires, the client attempts to renew its lease by sending a unicast DHCPREQUEST to the server that originally granted the lease.

Answer

25%

Answer

75%

Answer

87.5%

Question 7

Which TWO statements about the default administrative distances for different route sources are correct? (Choose TWO.)

Accepted Answer

The default administrative distance for a connected interface is 0.. Cisco IOS assigns default AD values to various route sources. Connected interfaces have an AD of 0, static routes have 1, EIGRP summary routes have 5, internal BGP has 200, and external EIGRP has 170. OSPF has 110, and RIP has 120. Knowing these defaults is critical for troubleshooting route selection.

Answer

The default administrative distance for internal BGP (iBGP) is 20.

Answer

The default administrative distance for RIP is 100.

Answer

The default administrative distance for OSPF is 90.

Question 8

An engineer configures IPv6 uRPF strict mode on an interface that is used for both IPv6 traffic and OSPFv3 routing. The router is an ABR with multiple areas. OSPFv3 adjacencies form correctly, but some IPv6 data traffic is dropped. The show ipv6 interface command shows uRPF is enabled. Which is the most likely explanation?

Accepted Answer

The router has a default route pointing to a different interface, and uRPF strict mode without 'allow-default' drops packets whose source address is reachable via the default route.. URPF strict mode on an interface checks that the source address of incoming packets is reachable via the same interface. If the router has a default route pointing to a different interface, packets sourced from addresses that are only reachable via that default route will fail the RPF check and be dropped. The 'allow-default' keyword is required to exempt packets whose source is reachable via a default route from this check.

Answer

OSPFv3 adjacencies use link-local addresses, which are not checked by uRPF, but data traffic uses global addresses that are incorrectly filtered by the OSPFv3 process.

Answer

The router has 'ipv6 uRPF allow-default' configured, but the default route is not installed, causing all traffic to be dropped.

Answer

The interface has an IPv6 ACL that denies traffic from certain prefixes, overriding uRPF.

Question 9

Which TWO commands would a network engineer use to verify that syslog messages are being sent to a remote syslog server? (Choose TWO.)

Accepted Answer

show logging. The 'show logging' command displays the current logging configuration, including the syslog server address and whether logging is enabled. The 'debug logging' command is not valid; the correct command to see real-time syslog messages is 'terminal monitor' after enabling logging. 'show run | include logging' shows the running config lines for logging. 'ping' tests reachability but not syslog functionality. 'show ip route' checks routing but not logging.

Answer

debug logging

Answer

ping <syslog-server-ip>

Answer

show ip route

Question 10

In MPLS L3VPN, what is the purpose of the Route Distinguisher (RD)?

Accepted Answer

To make IPv4 prefixes unique across different VRFs in the MPLS network.. The RD is an 8-byte value prepended to an IPv4 prefix to create a unique VPNv4 prefix. This allows overlapping IPv4 addresses from different VRFs to be carried in the same BGP table without conflict.

Answer

To control which VRFs import routes from other PEs.

Answer

To specify the VPN label that is used for forwarding.

Answer

To identify the VRF on the local PE router.

Question 11

An engineer is troubleshooting a router that is not sending syslog messages to the remote server at 192.168.1.10. The configuration includes 'logging host 192.168.1.10' and 'logging trap 7'. The router can ping 192.168.1.10. The engineer runs 'show logging' and sees 'Syslog logging: enabled (0 messages dropped, 0 messages rate-limited, 0 flushes, 0 overruns)'. What is the most likely cause?

Accepted Answer

The 'logging source-interface' is configured to an interface that is administratively down.. The 'show logging' output shows that syslog is enabled but no messages are being sent. A common reason is that the 'logging source-interface' is set to an interface that is down or not reachable, causing the router to use an incorrect source IP that the server may filter or that routing may not support. Alternatively, the server may be configured to accept messages only from specific source IPs.

Answer

The 'logging on' command is missing from the configuration.

Answer

The syslog server is using TCP, but the router is configured for UDP.

Answer

The logging buffer is full, preventing new messages from being generated.

Question 12

A network engineer is troubleshooting NAT for a VPN tunnel. The router has a static NAT rule 'ip nat inside source static 10.0.0.10 203.0.113.10' for a server. The VPN traffic from the remote site to 203.0.113.10 is being NATed to 10.0.0.10, but the return traffic from the server to the remote site is not being translated back. The engineer sees that the server sends packets with source 10.0.0.10 to the remote site's public IP. What should the engineer do to fix this?

Accepted Answer

Ensure that the router has a route to the remote site's public IP via the outside interface, and that the static NAT entry is correctly applied.. The issue is that the router lacks a route back to the remote site's public IP via the outside interface, or the static NAT entry is not correctly applied for the return traffic. Without a proper route, the router cannot determine that the return packets (from the inside server 10.0.0.10 to the remote public IP) should be translated back to 203.0.113.10. Ensuring the route exists and the static NAT is correctly configured allows the router to perform the reverse translation and forward the traffic out the outside interface.

Answer

Add an 'ip nat outside' command on the inside interface.

Answer

Configure a route-map to exempt the VPN traffic from NAT.

Answer

Change the static NAT to 'ip nat inside source static 10.0.0.10 203.0.113.10 extendable'.

Question 13

In an MPLS network, routers R1 and R2 are LDP neighbors with BFD enabled. R1#show mpls ldp neighbor shows R2 as 'Oper Down' for the BFD session. R2#show bfd neighbors shows the session with R1 as 'Down'. R1 and R2 have matching 'mpls ldp router-id' loopback0. The link between them is up. What is the root cause?

Accepted Answer

The LDP router-id must be the IP address of the interface where BFD is enabled.. BFD for LDP requires that the LDP session be established over the same interface as the BFD session. If the LDP router-id is not the interface IP used for BFD, the BFD session may fail. Here, the loopback0 is used as LDP router-id, but BFD is configured on the physical link, causing mismatch.

Answer

BFD is not supported with LDP on this platform.

Answer

The BFD interval is too low for LDP.

Answer

LDP must be configured with 'no bfd' to work properly.

Question 14

Which THREE statements about MPLS label operations (push, swap, pop) are true? (Choose THREE.)

Accepted Answer

The ingress LSR performs a label push operation.. In MPLS, the ingress LSR pushes a label, transit LSRs swap labels, and the penultimate hop router (PHP) pops the label. The egress LSR does not perform label operations if PHP is used. Label operations are based on the label forwarding table, not the routing table directly.

Answer

The egress LSR always performs a label pop operation.

Answer

Label operations are determined by the IP routing table.

Question 15

A network engineer runs the following command on Router R1:

R1# show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address       Client-ID/              Lease expiration        Type
                 Hardware address/
                 User name
192.168.1.10     0063.6973.636f.2e30.    Mar 01 2020 12:00 AM    Automatic
                 3030.3030.2e30.3030
                 312e.3130.3030.2e30
                 3030.312d.4574.682d
                 302f.31
192.168.1.11     0063.6973.636f.2e30.    Mar 01 2020 12:00 AM    Automatic
                 3030.3030.2e30.3030
                 312e.3130.3030.2e30
                 3030.312d.4574.682d
                 302f.31

Based on this output, which statement is correct?

Accepted Answer

The DHCP server has a duplicate client-id issue, likely caused by two clients using the same client identifier.. The output shows two DHCP bindings with identical client identifiers (the long hexadecimal string). This indicates that two clients are using the same client-ID, which violates RFC 2131 and causes the DHCP server to treat them as the same client, leading to duplicate address assignments or conflicts. Option B correctly identifies this duplicate client-id issue.

Answer

The DHCP server is functioning correctly with two unique bindings.

Answer

The DHCP server has run out of addresses in the pool.

Answer

The DHCP server is not assigning addresses because the lease time is set to 0.