Answers to Chapter 8 Review Questions

1:	Which of the following are valid representations for the address 200A 0000 0000 0C00 0000 0000 0000 0000 with a 60-bit prefix? 200A:0000:0000:0C/60 200A::0C00:0:0:0:0/60 200A:0000:0000:0C00::/60 200A::0C00::/60 200A:0:0:C00::/60 200A::0C/60
A:	B, C, E. A is not a complete address. D is ambiguous, with two sets of ::. F doesn't expand to the correct address.
2:	For what is the address 0:0:0:0:0:0:0:0 used?
A:	This is the unspecified address. It represents the absence of an address. If this is the source address of a packet, the interface has not yet been assigned an address. It is attempting to discover whether its tentative address is being used by another node.
3:	You configure your site border routers, connecting to an IPv6 public network, to advertise all your internal network numbers , including FEC0:0020:0:0100::/56. You get a nasty call from the IPv6 public network administrator. What is wrong?
A:	FEC0:0020:0:0100::/56 is a site-local address. It must never be advertised beyond the boundaries of a site.
4:	Which extension headers are processed by every IPv6 node in the path from source to destination?
A:	Hop-by-Hop.
5:	Which extension headers are used to specify a list of routers to visit before reaching the destination and to have each of those routers process the header?
A:	Destination Options header followed by the Routing header.
6:	A router receives a packet larger than its outgoing link's MTU. Does it fragment the packet and forward the fragments toward the destination?
A:	No. It drops the packet and sends an ICMP Packet Too Big message back to the source. The source uses these ICMP packets to perform path MTU discovery. It is the sole responsibility of the source to fragment the packet.
7:	If set in a Router Advertisement, what affect does the Managed bit have?
A:	The router sends the RA to all hosts on a link. If the Managed bit is set, the hosts obtain an address from a stateful configuration server.
8:	If a router advertises prefix information in its RAs, how is the information used?
A:	Prefix information included in RAs tells hosts which prefixes are on-link and/or which prefixes to use when they autoconfigure their addresses.
9:	In what two states can a host's IP address reside, and what are the roles of the two states?
A:	Preferred and deprecated. A preferred address can be used to initiate any IP session. A deprecated address should be used only to maintain an existing connection, not to initiate a new connection, if a preferred address exists.
10:	What information does a router advertise in its RA to tell hosts to stop using a particular prefix when initiating IP sessions?
A:	Either a Valid Lifetime or Preferred Lifetime of value 0. Valid Lifetime 0 says the prefix is no longer valid. Preferred Lifetime 0 says to deprecate the prefix.
11:	If a node has a neighbor with state DELAY, can the node send the neighbor packets?
A:	Yes. A neighbor with state DELAY has not been verified reachable , but the node will send packets to its cached link layer address for the neighbor.
12:	A host is not running any routing protocol. It is sending data to a remote node using a default router. The default router fails. Will the host continue to send data into the black hole of the dead router until its TCP connection fails?
A:	No. The neighbor unreachability process, default router list, and address resolution processes will assist the host in discovering the dead router and finding a new one.
13:	What are the scope values for multicast packets, and for what are they used?
A:	Node, link, site, organization, global. The scope values are used to limit the meaning of a multicast group and to control how far a multicast packet can travel.
14:	What Cisco router command enables IPv6 routing?
A:	ipv6 unicast-routing
15:	What interface subcommands enable IPv6 on an interface?
A:	ipv6 enable, ipv6 address address prefix [eui-64]
16:	What commands are used to enable a RIPng process?
A:	Interface subcommand: ipv6 rip process- name enable
17:	How is the BGP-for-IPv6 process enabled between neighbors?
A:	[click here] router bgp local-AS neighbor neighbor-ipv6-address remote-as remote-as-number ! address-family ipv6 neighbor neighbor-ipv6-address activate