MOD 7-9

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 Explanation: When a host boots and has been configured for dynamic IP addressing, the device tries to obtain a valid IP address. It sends a DHCPDISCOVER message. This is a broadcast message because the DHCP server address is unknown (by design). The destination IP address in the IP header is 255.255.255.255 and the destination MAC address is FF:FF:FF:FF:FF:FF.

Order the DHCP message types as they would occur between a DHCP client and a DHCP server. 1. DHCPDISCOVER 2. DHCPOFFER 3. DHCPREQUEST 4. DHCPACK 5. DHCPNACK

Explanation: 1. The DHCPDISCOVER message is used to identify any DHCP servers on a network. 2. The DHCPOFFER message is used by a server to offer a lease to a client. 3. The DHCPREQUEST message is used to identify both the specific DHCP server and the lease that the client is accepting. 4. The DHCPACK message is used by a server to finalize a successful lease with a client. 5. The DHCPNAK message is used when an offered lease is no longer valid.

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.

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

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.

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

- DHCPDISCOVER

Place the options in the following order: - a client initiating a message to find a DHCP server - DHCPDISCOVER - a DHCP server responding to the initial request by a client - DHCPOFFER - the client accepting the IP address provided by the DHCP server - DHCPREQUEST - the DHCP server confirming that the lease has been accepted - DHCPACK

- a client initiating a message to find a DHCP server - DHCPDISCOVER - a DHCP server responding to the initial request by a client - DHCPOFFER - the client accepting the IP address provided by the DHCP server - DHCPREQUEST - the DHCP server confirming that the lease has been accepted - DHCPACK

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.

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.

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.

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? (Choose two.) - DHCPDISCOVER - DHCPACK - DHCPOFFER - DHCPREQUEST - DHCPNAK

- DHCPDISCOVER - DHCPREQUEST Explanation: All DHCP messages between a DHCP-enabled client and a DHCP server are using broadcast messages until after the DHCPACK message. The DHCPDISCOVER and DHCPREQUEST messages are the only messages that are sent by a DHCP-enabled client. All DHCP messages between a DHCP-enabled client and a DHCP server use broadcast messages when the client is obtaining a lease for the first time.

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.

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: TimePort 49: TACACSPort 53: DNSPort 67: DHCP/BOOTP clientPort 68: DHCP/BOOTP serverPort 69: TFTPPort 137: NetBIOS name servicePort 138: NetBIOS datagram service

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.

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 server. - 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.

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.

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. Explanation: During the initial DHCP exchange between a client and server, the client broadcasts a DHCPDISCOVER message looking for DHCP servers. Multiple servers may be configured to respond to this request with DHCPOFFER messages. The client will choose the lease from one of the servers by sending a DHCPREQUEST message. It sends this message as a broadcast so that the other DHCP servers that sent offers will know that their offers were declined and the corresponding address can go back into the pool.

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.​

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

- 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 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.