300-410 DHCP (IPv4 and IPv6) Practice Test 2 — 15 Questions

Question 1

A network engineer runs the following command on Router R1:

R1# show ipv6 dhcp interface GigabitEthernet0/1
GigabitEthernet0/1 is in server mode
  Using pool: POOL6
  Preference value: 0
  Hint from client: ignored
  Rapid-Commit: disabled

Based on this output, which statement is correct?

Accepted Answer

The interface is configured as a DHCPv6 server using pool POOL6.. The command output explicitly states 'GigabitEthernet0/1 is in server mode' and 'Using pool: POOL6', which confirms that the interface is acting as a DHCPv6 server. The DHCPv6 server assigns IPv6 addresses and other configuration parameters from the specified pool to requesting clients.

Answer

The interface is configured as a DHCPv6 client.

Answer

The interface is using rapid-commit for faster address assignment.

Answer

The interface is in DHCPv6 relay mode.

Question 2

A network engineer runs the following command on Router R1:

R1# show ip dhcp relay information trusted
Interface                Trusted
GigabitEthernet0/1       Yes
GigabitEthernet0/2       No

Based on this output, which statement is correct?

Accepted Answer

DHCP relay information is trusted on GigabitEthernet0/1, so option 82 packets are accepted on that interface.. The command 'show ip dhcp relay information trusted' displays the trust status of each interface for DHCP relay information (option 82). When an interface is marked as 'Yes' under the Trusted column, it means the router will accept and forward DHCP packets that already contain option 82 information from that interface. Therefore, on GigabitEthernet0/1, option 82 packets are accepted.

Answer

DHCP relay information is trusted on both interfaces.

Answer

DHCP relay information is not configured on any interface.

Answer

DHCP relay information is trusted on GigabitEthernet0/2, so option 82 packets are dropped.

Question 3

A network engineer runs the following command on Router R1:

R1# show ip dhcp database
URL : flash:/dhcpdb
Read/write : Read/Write
Last updated : Mar 01 2020 00:00:00
Status : Last read succeeded. Next write scheduled in 0 seconds.

Based on this output, which statement is correct?

Accepted Answer

The DHCP database is stored in flash and is functioning correctly.. The output shows the DHCP database is stored in flash (URL: flash:/dhcpdb) with read/write access, and the status indicates the last read succeeded with a write scheduled in 0 seconds. This confirms the database is functioning correctly, as the router can read and write DHCP bindings to flash memory, which is the default storage location for DHCP database persistence.

Answer

The DHCP database is stored in NVRAM and is read-only.

Answer

The DHCP database write failed and needs to be rescheduled.

Answer

The DHCP database is empty because no bindings exist.

Question 4

Examine the following DHCP configuration on router R1:

ip dhcp excluded-address 192.168.1.1 192.168.1.10
!
ip dhcp pool POOL1
 network 192.168.1.0 255.255.255.0
 default-router 192.168.1.1
 dns-server 8.8.8.8
 lease 0 2 30
!
interface GigabitEthernet0/0
 ip address 192.168.1.1 255.255.255.0
 ip helper-address 192.168.2.2
 no shutdown

What is the effect of this configuration?

Accepted Answer

Clients on the 192.168.1.0/24 subnet will receive IP addresses from the local DHCP pool, and the ip helper-address will forward DHCP requests to 192.168.2.2, causing duplicate offers.. Option A is correct because the router R1 is configured as a DHCP server for the 192.168.1.0/24 subnet via the local pool POOL1, and the ip helper-address 192.168.2.2 on the same interface will forward broadcast DHCP requests from clients to the remote DHCP server at 192.168.2.2. This results in both the local pool and the remote server offering IP addresses, leading to duplicate offers on the subnet.

Answer

The ip helper-address command will be ignored because the router is the DHCP server for that subnet.

Answer

The excluded-address range is misconfigured because it includes the router's own interface IP, which will prevent the router from functioning.

Answer

The DHCP pool will not assign addresses because the network statement does not match the interface subnet exactly.

Question 5

Consider the following DHCPv6 configuration on router R2:

ipv6 dhcp pool DHCP6_POOL
 dns-server 2001:db8::1
 domain-name example.com
!
interface GigabitEthernet0/0
 ipv6 address 2001:db8:1::1/64
 ipv6 dhcp server DHCP6_POOL
 ipv6 nd other-config-flag
 no shutdown

What is the effect of this configuration?

Accepted Answer

Hosts on this subnet will use SLAAC to obtain their IPv6 address and then use DHCPv6 to get DNS and domain information.. Option A is correct because the configuration uses the `ipv6 nd other-config-flag` command, which sets the 'Other Configuration' flag (O-flag) in Router Advertisement (RA) messages. This tells hosts to use Stateless Address Autoconfiguration (SLAAC) for their IPv6 address (based on the prefix in the RA) and then use DHCPv6 (stateless DHCPv6) only to obtain additional parameters like DNS server and domain name, as defined in the DHCPv6 pool.

Answer

Hosts will obtain both their IPv6 address and DNS information from the DHCPv6 pool.

Answer

The DHCPv6 pool is missing the address prefix, so it will not provide any configuration to clients.

Answer

The ipv6 nd other-config-flag command is ignored because the DHCPv6 server is configured on the interface.

Question 6

Router R3 has the following DHCP configuration:

ip dhcp pool POOL2
 network 10.10.10.0 255.255.255.0
 default-router 10.10.10.1
 dns-server 10.10.10.2
 lease 7
!
interface GigabitEthernet0/0
 ip address 10.10.10.1 255.255.255.0
 ip dhcp relay information option
 no shutdown

What is the problem with this configuration?

Accepted Answer

The relay information option should not be configured on the server interface; it is intended for relay agents and may cause DHCP packets to be dropped or misprocessed.. The 'ip dhcp relay information option' command is intended for DHCP relay agents to insert Option 82 (Relay Agent Information) into DHCP packets. When configured on a DHCP server interface, it causes the server to expect and process Option 82, but since the server itself is not a relay agent, this can lead to malformed packets, dropped requests, or misprocessing of DHCP messages. In this scenario, R3 is acting as the DHCP server on GigabitEthernet0/0, so the command should be removed to ensure normal DHCP operation.

Answer

The lease duration of 7 days is invalid; valid lease values are in hours or minutes only.

Answer

The default-router address is missing the subnet mask, which will cause clients to receive an incomplete configuration.

Answer

The DNS server address is on the same subnet as the clients, which is not allowed.

Question 7

Router R4 has the following DHCPv6 configuration:

ipv6 dhcp pool DHCP6_POOL2
 address prefix 2001:db8:2::/64
 dns-server 2001:db8::1
!
interface GigabitEthernet0/1
 ipv6 address 2001:db8:2::1/64
 ipv6 dhcp server DHCP6_POOL2
 ipv6 nd managed-config-flag
 no shutdown

What is the effect of this configuration?

Accepted Answer

Hosts will use DHCPv6 to obtain both their IPv6 address and other configuration parameters like DNS.. The configuration uses the `ipv6 nd managed-config-flag` command, which sets the Managed Address Configuration flag (M flag) in Router Advertisement (RA) messages. When the M flag is set to 1, hosts are instructed to use DHCPv6 (stateful DHCPv6) to obtain their IPv6 addresses, not SLAAC. Additionally, the DHCPv6 pool provides DNS server information, so hosts will use DHCPv6 for both addressing and other configuration parameters like DNS. This matches option A.

Answer

Hosts will use SLAAC for addressing and DHCPv6 for DNS only.

Answer

The DHCPv6 pool is missing a domain-name, so it will not provide any configuration.

Answer

The ipv6 nd managed-config-flag command is incompatible with the DHCPv6 server and will cause an error.

Question 8

Router R5 has this DHCP configuration:

ip dhcp pool POOL3
 network 172.16.0.0 255.255.255.0
 default-router 172.16.0.1
 option 150 ip 10.10.10.10
!
interface GigabitEthernet0/0
 ip address 172.16.0.1 255.255.255.0
 no shutdown

What is the purpose of the option 150 command?

Accepted Answer

It provides the IP address of a TFTP server to DHCP clients, typically used by VoIP phones.. Option 150 is a DHCP option that specifies the IP address of a TFTP server. Cisco IP phones use this option to locate the TFTP server from which they download their configuration and firmware files. The correct answer is A because this is the standard purpose of option 150 in a Cisco VoIP environment.

Answer

It sets the DNS server for the DHCP pool.

Answer

It defines a custom option that is ignored by standard DHCP clients.

Answer

It specifies the default gateway for the clients.

Question 9

Router R6 has the following DHCPv6 configuration:

ipv6 dhcp pool DHCP6_POOL3
 address prefix 2001:db8:3::/64 lifetime 3600 600
 dns-server 2001:db8::1
!
interface GigabitEthernet0/2
 ipv6 address 2001:db8:3::1/64
 ipv6 dhcp server DHCP6_POOL3
 ipv6 nd managed-config-flag
 no shutdown

What is the effect of the lifetime parameters 3600 and 600?

Accepted Answer

The preferred lifetime is 3600 seconds and the valid lifetime is 600 seconds, which is invalid because the valid lifetime must be greater than or equal to the preferred lifetime.. Option A is correct because in the `ipv6 dhcp pool` configuration, the `lifetime` command specifies the preferred lifetime first (3600 seconds) and the valid lifetime second (600 seconds). According to RFC 4862, the valid lifetime must be greater than or equal to the preferred lifetime; otherwise, the configuration is invalid and will be rejected by the router. This mismatch causes the DHCPv6 pool to fail to apply the prefix.

Answer

The preferred lifetime is 600 seconds and the valid lifetime is 3600 seconds, which is a typical configuration.

Answer

The lifetimes are applied to the DNS server address, not the address prefix.

Answer

The configuration is valid and will work as expected.

Question 10

What is the default lease duration for a DHCPv4 address pool on a Cisco IOS router?

Accepted Answer

1 day. The default lease duration for a DHCPv4 address pool on a Cisco IOS router is 1 day (86400 seconds). This is defined by the Cisco IOS DHCP server implementation, which uses a 24-hour lease as the default when no lease duration is explicitly configured under the DHCP pool configuration.

Answer

7 days

Answer

30 minutes

Answer

Infinite

Question 11

In DHCPv6, what is the purpose of the 'managed-config-flag' in Router Advertisement messages?

Accepted Answer

It indicates that hosts should use DHCPv6 to obtain their IPv6 address and other configuration parameters.. The 'managed-config-flag' (M flag) in Router Advertisement (RA) messages, as defined in RFC 3315 and RFC 4861, tells hosts to use stateful DHCPv6 for both IPv6 address assignment and other configuration parameters (e.g., DNS servers). When set to 1, hosts must use DHCPv6 to obtain their IPv6 address, overriding SLAAC for addressing. This flag is part of the RA's prefix information option and directly controls whether hosts perform stateful or stateless address configuration.

Answer

It indicates that hosts should use SLAAC for addressing and DHCPv6 for other configuration only.

Answer

It indicates that the router is a DHCPv6 server.

Answer

It indicates that hosts should use only stateless address autoconfiguration.

Question 12

Which DHCP message type is used by a client to renew its lease before it expires?

Accepted Answer

DHCPREQUEST. When a DHCP client wants to renew its existing lease before it expires, it sends a unicast DHCPREQUEST message directly to the DHCP server that originally granted the lease. This is part of the renewal process defined in RFC 2131, where the client transitions from the BOUND state to the RENEWING state and uses the server's IP address to request an extension of the lease time.

Answer

DHCPDISCOVER

Answer

DHCPACK

Answer

DHCPRELEASE

Question 13

Which TWO commands can be used to verify DHCP IPv4 server operation and address pool utilization on a Cisco IOS router? (Choose TWO.)

Accepted Answer

show ip dhcp binding. Option A is correct because the 'show ip dhcp binding' command displays the list of active DHCP address bindings, including the IP address, MAC address, lease expiration, and type (automatic, manual, or dynamic). This directly verifies that the DHCP server is operating and has allocated addresses from its pool. Option B is correct because the 'show ip dhcp pool' command shows the pool name, utilization statistics (e.g., total addresses, leased addresses, and excluded addresses), and pool configuration, confirming address pool utilization.

Answer

show ip dhcp conflict

Answer

debug ip dhcp server events

Answer

show ip interface

Question 14

Which TWO statements about DHCP IPv6 (DHCPv6) operation are true? (Choose TWO.)

Accepted Answer

DHCPv6 servers listen on UDP port 547.. DHCPv6 servers listen on UDP port 547, while DHCPv6 clients use UDP port 546. This is defined in RFC 3315 and is a key distinction from DHCPv4, where servers listen on port 67 and clients on port 68. The server uses port 547 to receive requests from clients, ensuring proper separation of DHCPv6 traffic.

Answer

DHCPv6 can only be used in stateless mode.

Answer

DHCPv6 uses UDP ports 67 and 68, just like DHCPv4.

Answer

DHCPv6 relies on ARP to discover DHCPv6 servers.

Question 15

Which THREE symptoms indicate a DHCP IPv4 starvation attack or address pool exhaustion? (Choose THREE.)

Accepted Answer

Legitimate clients fail to obtain an IP address via DHCP.. Option A is correct because a DHCP starvation attack exhausts the available IP addresses in the pool, preventing legitimate clients from obtaining a lease. When the address pool is fully depleted, the DHCP server cannot respond to new DISCOVER messages, causing clients to fail to acquire an IP address.

Answer

Client devices experience high CPU utilization due to DHCP processing.

Answer

Duplicate IP address detection (DAD) failures are reported on all clients.