ccna 200 301 ebook

ccna 200 301 ebook.engineer has called the user and asked him to issue some commands, and then the engineer believes that the host is trying to dynamically learn its IPv6 settings and that the host does not yet have an IPv6 unicast address.For the sake of discussion, assume that this network uses such a strategy for assigning IPv6 addresses, which is done through DHCPv6. The engineer is aware of this strategy, so he is already thinking about why this process is failing. This scenario walks you through several problems caused by simple, straightforward errors.Tip: This book ignores the details of a process that tells a host to use SLAAC or stateful DHCPv6. to keep the discussion pure and stay within the scope of this book, we assume, for this discussion, that only stateful DHCP is used.Troubleshooting stateful DHCP follows the same basic logic as IPv4 DHCP, as discussed in Chapter 5, "Troubleshooting IPv4 Selective Routing," in the "DHCP Relay Issues" section. So, repeating the rules presented in Chapter 5, for an IPv6 host to successfully use stateful or stateless DHCPv6,to DHCPV6 server information, the following conditions must be met.(D The server must be on the same subnet as the client. (2) The server may be on a different subnet while.a-Router on the same subnet as the client host correctly implements DHCP relay. The connection between the local router (the router closer to the client host) and the DHCPv6 server is an IPv6 connection. b-Local router (the router closer to the client host) and the DHCPv6 server. The two most likely root causes of a host's inability to dynamically learn its IPv6 settings through stateful DHCPv6 are 2a and 2b. for2a, the solution requires the correct interface to be configured with commands on each LAN other than the LAN on which the DHCPv6 server resides. For example, in Figure 16-16, Host D is on the left LAN subnet while R1's G0/0 interface is connected to the same subnet. Rl should use the commands listed at the bottom of the figure toStart the IPv6 DHCP relay function that points to the DHCPv6 server on the right. If Rl does not execute the ipv6dhcprelay command or if the command points to the wrong IPv6 address, Host D's attempt to use DHCPv6 will fail.The item listed in 2b is not actually the root cause. Rather, it is simply a symptom of another problem that requires further investigation. A connection must exist between Rl and the DHCPv6 server and be able to return to the address that Rl used to find the source of the DHCPv6 message. (Rl finds the DHCPv6 request from the output interface where the message was sent, not necessarily the one configured using the ipv6 dhcp relay command. In this example, Rl would use its serial interface IPv6 address.) The best way to test for this issue is by Rlping the IPv6 address of the DHCPv6 server from theThe host drops the IPv6 setting: the SLAAC problem