RSE CCNA 2 Chapter 8 Quiz Online

DHCPv6 hosts will send a DHCP SOLICIT message to the all DHCP routers multicast address of FF02::1:2.

This router should be configured with the ip helper-address command, followed with the IP address of the DHCPv4 server, because the router is meant to be used as a relay agent. The ip dhcp pool RELAY command just names the DHCPv4 pool, and it does not enable the relay function.

Because a DHCP client does not have a valid IPv4 address, it must use a broadcast IP address of 255.255.255.255 as the destination address to communicate with the DHCP server. The DHCPDISCOVER message sent by the client is the first message sent in order to make initial contact with a DHCP server.

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.

SOHO and home broadband routers are typically set to acquire an IPv4 address automatically from the ISP. The IP address that is assigned is typically a dynamic address to reduce the cost, but a static IP address is possible with more cost. However, if the router is assigned a dynamic IP address, DNS issues will result in the web server behind the router not being easily accessible to the public. Routers are typically also gateways for LANs, but this has no bearing on whether the router is configured as a DHCP client on its WAN link or not. Likewise, a router can be configured to be a DHCP client in order to obtain an IP address from the ISP, but at the same time, it can be configured as a DHCP server to serve the IP addressing for the devices on its LAN.

The Managed Address Configuration (M) flag and the Other Configuration (O) flag in ICMPv6 RA messages are used to indicate to an IPv6 client how it should configure its IPv6 addresses. If the M flag is set to 0 it means that the host should automatically configure its own IPv6 interface address rather than asking for one from a DHCPv6 server. If the O flag is set to 1, it means that the client can find additional addressing information, such as a DNS server address, by contacting a DHCPv6 server after it has automatically configured its own address.

Stateless Address Autoconfiguration (SLAAC) can be used as an alternative to DHCPv6. In this approach, a router provides global routing prefix, prefix length, default gateway, and DNS server information to a host. The host is not provided with a global unicast address by SLAAC. Instead, SLAAC suggests that the host create its own global unicast address based on the supplied global routing prefix. ARP is not used in IPv6. ICMPv6 messages are used by SLAAC to provide addressing and other configuration information. EUI-64 is a process in which a host will create an Interface ID from its 48-bit MAC address.

The show ip dhcp binding command will show the leases, including IP addresses, MAC addresses, lease expiration, type of lease, client ID, and user name.

The ipv6 dhcp relay command must be applied to the interface where the clients are located. The ipv6 dhcp relay command can use either the link-local or global unicast address of the DHCPv6 server, or even a multicast address. The ipv6 nd managed-config-flag indicates to the clients that they should use stateful DHCPv6 and is also applied to the interface where the clients are located.

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.

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.

Before an IPv6 host can enable and use an assigned IPv6 address, the host must verify that the address is unique on the network. To verify that no other hosts are using the IPv6 address, the host performs the duplicate address detection (DAD) process by sending a Neighbor Solicitation (NS) message to the IPv6 address.

The debug ip dhcp server events command reports IP address assignments and database updates as they happen.

The broadcast DHCPDISCOVER message finds DHCPv4 servers on the network. When the DHCPv4 server receives a DHCPDISCOVER message, it reserves an available IPv4 address to lease to the client and sends the unicast DHCPOFFER message to the requesting client. When the client receives the DHCPOFFER from the server, it sends back a DHCPREQUEST. On receiving the DHCPREQUEST message the server replies with a unicast DHCPACK message. DHCPREPLY and DHCPINFORMATION-REQUEST are DHCPv6 messages.

When the ipv6 address dhcp command is configured on a router interface, it enables the router as a DHCPv6 client on this interface. The ipv6 enable command enables IPv6 on an interface and allows the router to configure its link-local address. The ipv6 address autoconfigure command tells the router to use either SLAAC or stateless DHCPv6 to configure its global unicast address. The ipv6 dhcp server command is used on a router that is running a DHCPv6 server to indicate what address information should be served to clients.