CCNA Ch 7-9

The ________________ message is used when an offered lease is no longer valid.

DHCPNAK

The ____________ message is used by a server to offer a lease to a client.

DHCPOFFER

the client accepting the IP address provided by the DHCP server

DHCPREQUEST

Which message does an IPv4 host use to reply when it receives a DHCPOFFER message from a DHCP server? DHCPOFFER DHCPDISCOVER DHCPREQUEST DHCPACK

DHCPREQUEST Explanation: When the client receives the DHCPOFFER from the server, it sends back a DHCPREQUEST broadcast message. On receiving the DHCPREQUEST message, the server replies with a unicast DHCPACK message.

Refer to the exhibit. What protocol can be configured on gateway routers R1 and R2 that will allow traffic from the internal LAN to be load balanced across the two gateways to the Internet? GLBP PVST+ PVST STP

GLBP Explanation: GLBP, or Group Load Balancing Protocol, allows multiple routers to act as a single default gateway for hosts. GLBP load balances the traffic across the individual routers on a per host basis.

What is an advantage of configuring a Cisco router as a relay agent? - It can provide relay services for multiple UDP services. - It reduces the response time from a DHCP server. - It can forward both broadcast and multicast messages on behalf of clients. - It will allow DHCPDISCOVER messages to pass without alteration.

It can provide relay services for multiple UDP services. Explanation: By default, the ip helper-address command forwards the following eight UDP services: Port 37: Time Port 49: TACACS Port 53: DNS Port 67: DHCP/BOOTP client Port 68: DHCP/BOOTP server Port 69: TFTP Port 137: NetBIOS name service Port 138: NetBIOS datagram service

23. Question as presented:

A stateless DHCPv6 client would send a DHCPv6 INFORMATION-REQUEST message as step 3 in the process.

Which protocol automates assignment of IP addresses on a network, and which port number does it use? (Choose two.) DHCP DNS SMB 53 67 80

DHCP; 67 (Explanation: DNS uses port 53 and translates URLs to IP addresses. SMB provides shared access to files and printers and uses port 445. Port 80 is used by HTTP. HTTP is a protocol used to communicate between a web browser and a server.)

The ______________ message is used by a server to finalize a successful lease with a client.

DHCPACK

a client initiating a message to find a DHCP server.

DHCPDISCOVER

a DHCP server responding to the initial request by a client

DHCPOFFER

A company uses the SLAAC method to configure IPv6 addresses for the employee workstations. Which address will a client use as its default gateway?​ - the global unicast address of the router interface that is attached to the network - the unique local address of the router interface that is attached to the network - the all-routers multicast address - the link-local address of the router interface that is attached to the network

the link-local address of the router interface that is attached to the network Explanation: When a PC is configured to use the SLAAC method for configuring IPv6 addresses, it will use the prefix and prefix-length information that is contained in the RA message, combined with a 64-bit interface ID (obtained by using the EUI-64 process or by using a random number that is generated by the client operating system), to form an IPv6 address. It uses the link-local address of the router interface that is attached to the LAN segment as its IPv6 default gateway address.

Refer to the exhibit. A network engineer is troubleshooting host connectivity on a LAN that uses a first hop redundancy protocol. Which IPv4 gateway address should be configured on the host? 192.168.2.0 192.168.2.1 192.168.2.2 192.168.2.100

192.168.2.100 Explanation: The host default gateway address should be the FHRP (in this case GLBP) virtual IP address.

Refer to the exhibit. PC1 is configured to obtain a dynamic IP address from the DHCP server. PC1 has been shut down for two weeks. When PC1 boots and tries to request an available IP address, which destination IP address will PC1 place in the IP header? - 192.168.1.1 - 192.168.1.255 - 255.255.255.255 - 192.168.1.8

255.255.255.255

A network administrator is analyzing the features that are supported by different first-hop router redundancy protocols. Which statement describes a feature that is associated with HSRP? - HSRP uses active and standby routers. - HSRP is nonproprietary. - It allows load balancing between a group of redundant routers. - It uses ICMP messages in order to assign the default gateway to hosts.

HSRP uses active and standby routers. Explanation: The HSRP first-hop router redundancy protocol is Cisco proprietary and supports standby and active devices. VRRPv2 and VRRPv3 are nonproprietary. GLBP is Cisco proprietary and supports load balancing between a group of redundant routers.

A client device on an Ethernet segment needs an IP address in order to communicate on the network. A DHCP server with IP address 192.168.1.1 has been configured and enabled on the network. How will a client device obtain a usable IP address for this network? - Send a DHCPACK packet to the default gateway address. - Use a statically configured IP address from the pool of IP addresses that is offered by the DHCP servterm-19er. - Send a DHCPDISCOVER message to physical address FF-FF-FF-FF-FF-FF. - Send a DHCPREQUEST packet to IP address 255.255.255.255.

Send a DHCPDISCOVER message to physical address FF-FF-FF-FF-FF-FF. Explanation: Like IP addressing, there is also a special MAC address for broadcast purposes: FF-FF-FF-FF-FF-FF. When a DHCP client needs to send a DHCP Discover message in order to seek DHCP servers, the client will use this MAC address as the destination MAC address in the Ethernet frame. It does this because it has no knowledge of the IP and MAC addresses of DHCP servers.

Refer to the exhibit. A network administrator is configuring a router for DHCPv6 operation. Which conclusion can be drawn based on the commands? - The router is configured for stateful DHCPv6 operation, but the DHCP pool configuration is incomplete. - The DHCPv6 server name is ACAD_CLASS. - Clients would configure the interface IDs above 0010. - The router is configured for stateless DHCPv6 operation.

The router is configured for stateless DHCPv6 operation. Explanation: The DHCPv6 is for the stateless DHCPv6 operation that is indicated by changing the O flag to 1 and leaving the M flag as default, which is 0. Therefore, it is not configured for stateful DHCPv6 operation. Although the DNS server has the interface ID 0010, clients in stateless DHCPv6 operation will configure their interface IDs either by EUI-64 or a random number. The ACAD_CLASS is the name of the DHCP pool, not the DHCP server name.

An administrator issues the commands: - Router(config)# interface g0/1 - Router(config-if)# ip address dhcp What is the administrator trying to achieve? configuring the router to act as a DHCPv4 server configuring the router to obtain IP parameters from a DHCPv4 server configuring the router to act as a relay agent configuring the router to resolve IP address conflicts

configuring the router to obtain IP parameters from a DHCPv4 server

Which command, when issued in the interface configuration mode of a router, enables the interface to acquire an IPv4 address automatically from an ISP, when that link to the ISP is enabled? service dhcp ip address dhcp ip helper-address ip dhcp pool

ip address dhcp Explanation: The ip address dhcp interface configuration command configures an Ethernet interface as a DHCP client. The service dhcp global configuration command enables the DHCPv4 server process on the router. The ip helper-address command is issued to enable DHCP relay on the router. The ip dhcp pool command creates the name of a pool of addresses that the server can assign to hosts.

A DHCP-enabled client PC has just booted. During which two steps will the client PC use broadcast messages when communicating with a DHCP server? DHCPDISCOVER DHCPACK DHCPOFFER DHCPREQUEST DHCPNAK

DHCPREQUEST DHCPDISCOVER

Refer to the exhibit. What should be done to allow PC-A to receive an IPv6 address from the DHCPv6 server? - Add the ipv6 dhcp relay command to interface Fa0/0. - Change the ipv6 nd managed-config-flag command to ipv6 nd other-config-flag. - Configure the ipv6 nd managed-config-flag command on interface Fa0/1. - Add the IPv6 address 2001:DB8:1234:5678::10/64 to the interface configuration of the DHCPv6 server.

Add the ipv6 dhcp relay command to interface Fa0/0. Explanation: Client DHCPv6 messages are sent to a multicast address with link-local scope, which means that the messages will not be forwarded by routers. Because the client and server are on different subnets on different interfaces, the message will not reach the server. The router can be configured to relay the DHCPv6 messages from the client to the server by configuring the ipv6 dhcp relay command on the interface that is connected to the client.

the DHCP server confirming that the lease has been accepted

DHCPACK

A host PC is attempting to lease an address through DHCP. What message is sent by the server to let the client know it is able to use the provided IP information? DHCPDISCOVER DHCPOFFER DHCPREQUEST DHCPACK DHCPNACK

DHCPACK Explanation: When a host uses DHCP to automatically configure an IP address, the typically sends two messages: the DHCPDISCOVER message and the DHCPREQUEST message. These two messages are usually sent as broadcasts to ensure that all DHCP servers receive them. The servers respond to these messages using DHCPOFFER, DHCPACK, and DHCPNACK messages, depending on the circumstance.

The _____________ message is used to identify any DHCP servers on a network.

DHCPDISCOVER

Which DHCP IPv4 message contains the following information? Destination address: 255.255.255.255 Client IPv4 address: 0.0.0.0 Default gateway address: 0.0.0.0 Subnet mask: 0.0.0.0 DHCPACK DHCPDISCOVER DHCPOFFER DHCPREQUEST

DHCPDISCOVER

A small coffee shop is offering free Wi-Fi to customers. The network includes a wireless router and a DSL modem that is connected to the local phone company. What method is typically used to configure the connection to the phone company? - Set the WAN connection in the wireless router as a DHCP client. - Set the connection between the wireless router and the DSL modem as a private IP network. - Set the DSL modem as a DHCP client to get a public IP address from the wireless router. - Set the DSL modem as a DHCP client to the phone company and a DHCP server for the internal connection.

Set the WAN connection in the wireless router as a DHCP client. Explanation: In a SOHO environment, a wireless router connects to an ISP via a DSL or cable modem. The IP address between the wireless router and ISP site is typically assigned by the ISP through DHCP. The DSL modem does not manage IP address allocation.

Which statement is true about DHCP operation?​ - When a device that is configured to use DHCP boots, the client broadcasts a DHCPDISCOVER message to identify any available DHCP servers on the network.​ - A client must wait for lease expiration before it sends another DHCPREQUEST message.​ - If the client receives several DHCPOFFER messages from different servers, it sends a unicast DHCPREQUEST message to the server from which it chooses to obtain the IP information. - The DHCPDISCOVER message contains the IP address and subnet mask to be assigned, the IP address of the DNS server, and the IP address of the default gateway.​

When a device that is configured to use DHCP boots, the client broadcasts a DHCPDISCOVER message to identify any available DHCP servers on the network.​ Explanation: The client broadcasts a DHCPDISCOVER message to identify any available DHCP servers on the network. A DHCP server replies with a DHCPOFFER message. This message offers to the client a lease that contains such information as the IP address and subnet mask to be assigned, the IP address of the DNS server, and the IP address of the default gateway. After the client receives the lease, the received information must be renewed through another DHCPREQUEST message prior to the lease expiration.

Which DHCPv4 message will a client send to accept an IPv4 address that is offered by a DHCP server? broadcast DHCPACK broadcast DHCPREQUEST unicast DHCPACK unicast DHCPREQUEST

broadcast DHCPREQUEST Explanation: When a DHCP client receives DHCPOFFER messages, it will send a broadcast DHCPREQUEST message for two purposes. First, it indicates to the offering DHCP server that it would like to accept the offer and bind the IP address. Second, it notifies any other responding DHCP servers that their offers are declined.

The __________________ message is used to identify both the specific DHCP server and the lease that the client is accepting.

DHCPREQUEST

A network administrator configures a router to send RA messages with M flag as 0 and O flag as 1. Which statement describes the effect of this configuration when a PC tries to configure its IPv6 address? - It should contact a DHCPv6 server for the prefix, the prefix-length information, and an interface ID that is both random and unique. - It should use the information that is contained in the RA message and contact a DHCPv6 server for additional information. - It should use the information that is contained in the RA message exclusively. - It should contact a DHCPv6 server for all the information that it needs.

It should use the information that is contained in the RA message and contact a DHCPv6 server for additional information. Explanation: ICMPv6 RA messages contain two flags to indicate whether a workstation should use SLAAC, a DHCPv6 server, or a combination to configure its IPv6 address. These two flags are M flag and O flag. When both flags are 0 (by default), a client must only use the information in the RA message. When M flag is 0 and O flag is 1, a client should use the information in the RA message and look for the other configuration parameters (such as DNS server addresses) on DHCPv6 servers.

When a client is requesting an initial address lease from a DHCP server, why is the DHCPREQUEST message sent as a broadcast? - The client does not yet know the IP address of the DHCP server that sent the offer. - The DHCP server may be on a different subnet, so the request must be sent as a broadcast. - The client does not have a MAC address assigned yet, so it cannot send a unicast message at Layer 2. - The client may have received offers from multiple servers, and the broadcast serves to implicitly decline those other offers.

The client may have received offers from multiple servers, and the broadcast serves to implicitly decline those other offers.

What is one indication that a Windows computer did not receive an IPv4 address from a DHCP server? - The computer cannot ping 127.0.0.1. - The computer receives an IP address that starts with 169.254. - Windows displays a DHCP timeout message. - The computer cannot ping other devices on the same network with IP addresses in the 169.254.0.0/16 range.

The computer receives an IP address that starts with 169.254. Explanation: When a Windows PC cannot communicate with an IPv4 DHCP server, the computer automatically assigns an IP address in the 169.254.0.0/16 range. Any other device on the same network that receives an address in the same range is reachable.​

Refer to the exhibit. A network administrator is implementing the stateless DHCPv6 operation for the company. Clients are configuring IPv6 addresses as expected. However, the clients are not getting the DNS server address and the domain name information configured in the DHCP pool. What could be the cause of the problem? - The DNS server address is not on the same network as the clients are on. - The router is configured for SLAAC operation. - The GigabitEthernet interface is not activated. - The clients cannot communicate with the DHCPv6 server, evidenced by the number of active clients being 0.

The router is configured for SLAAC operation. Explanation: The router is configured for SLAAC operation because there is no configuration command to change the RA M and O flag value. By default, both M and O flags are set to 0. In order to permint stateless DHCPv6 operation, the interface command ipv6 nd other-config-flag should be issued. The GigabitEthernet interface is in working condition because clients can get RA messages and configure their IPv6 addresses as expected. Also, the fact that R1 is the DHCPv6 server and clients are getting RA messages indicates that clients can communicate with the DHCP server. The number of active clients is 0 because the DHCPv6 server does not maintain the state of clients IPv6 addresses (it is not configured for stateful DHCPv6 operation). The DNS server address issue is not relevant to the problem.

Which kind of message is sent by a DHCP client when its IP address lease has expired?​ a DHCPDISCOVER unicast message​ a DHCPREQUEST broadcast message​ a DHCPREQUEST unicast message​ a DHCPDISCOVER broadcast message

a DHCPREQUEST unicast message​ Explanation: When the IP address lease time of the DHCP client expires, it sends a DHCPREQUEST unicast message directly to the DHCPv4 server that originally offered the IPv4 address.

A company uses DHCP to manage IP address deployment for employee workstations. The IT department deploys multiple DHCP servers in the data center and uses DHCP relay agents to facilitate the DHCP requests from workstations. Which two UDP ports are used to forward DHCP traffic? (Choose two.) - 23 - 53 - 67 - 68 - 80

67, 68 Explanation: The DHCP protocol operates with 2 UDP ports. UDP port 67 is the destination port for DHCP servers, and DHCP clients use UDP port 68.