Chapter 21

"Do I Know This Already?"

1.B and C
5.C and D


1.Cisco routers support RIPng, EIGRP for IPv6, IS-IS for IPv6, MP-BGP4, and OSPFv3. Static routes are also supported.
2.Like its predecessor OSPFv2, OSPFv3 is a link-state routing protocol that uses the Dijkstra SPF algorithm to select best paths through the network.
3.The link-local address, autoconfigured using the FE80::/10 prefix, is used as the source addresses in an OSPFv3 hello packet.
4.OSPFv3 is different from OSPFv2 in many ways, including the following:
  • Has 128-bit prefix support and runs within IPv6 packets; however, still uses 32-bit router ID, area ID and link-state ID

  • Uses multicast addresses FF02::5 and FF02::6

  • Uses links rather than subnets; uses link-local address as source address

  • Has a 16-byte packet header; authentication not built-in, uses IPv6 extension headers instead

  • Support for multiple instances

5.Type 1 is a Router-LSA; type 9 is an Intra-Area-Prefix-LSA, new to OSPFv3.

In OSPFv3, LSA types 1 and 2 no longer contain route prefixes, instead they contain 32-bit IDs. OSPFv3 type 3 and type 9 LSAs carry all IPv6 prefix information; in OSPFv2, IPv4 prefix information is carried in type 1 and type 2 LSAs (router and network LSAs).

6.OSPFv3 priority works the same way it does for OSPFv2—routers default to a priority of 1; a higher priority means a better chance of being elected DR or BDR, and 0 means that the router will not serve as a DR or BDR.
7.The commands used to implement IPv6 and OSPFv3 are as follows:
RouterA(config)#ipv6 unicast-routing
RouterA(config)#ipv6 cef
RouterA(config)#ipv6 router ospf 1
RouterA(config-rtr)#interface fastethernet0/0
RouterA(config-if)#ipv6 address 2001:0:1:1::2/64
RouterA(config-if)#ipv6 ospf 1 area 1
RouterA(config-if)#interface serial 1/0
RouterA(config-if)#ipv6 address 2001:0:1:5::1/64
RouterA(config-if)#ipv6 ospf 1 area 1
8.The following command is used to configure an OSPFv3 router ID:
Router(config-rtr)#router-id 32-bit-router-id

The router ID must be a 32-bit number in an IPv4-address dotted decimal format, and could be set to the value of an IPv4 address on the router.

9.Interfaces are assigned to areas in OSPFv3 in interface configuration mode, using the ipv6 ospf process-id area area-id [instance instance-id] command, instead of using the network command in router configuration mode, as is done for OSPFv2.
10.The show ipv6 ospf neighbor or show ipv6 ospf neighbor detail command can be used to verify that neighbor relationships have been established with the appropriate directly connected routers.
11.There are several transition mechanisms including
  • Dual Stack

  • Tunneling (manual, 6-to-4, ISATAP, and Teredo)

  • Translation

12.The commands used to implement IPv4 and IPv6 are as follows:
RouterA(config)#ipv6 unicast-routing
RouterA(config)#ipv6 cef
RouterA(config)#interface fastethernet0/0
RouterA(config-if)#ip address
RouterA(config-if)#ipv6 address 2001:1:A:ABCD::1/64
RouterA(config-if)#interface fastethernet0/1
RouterA(config-if)#ip address
RouterA(config-if)#ipv6 address 2001:1:A:FEDC::1/64

13.The 6-to-4 prefix is 2002:AC14.40C0, because AC14.40C0 is the hexadecimal representation of
14.NAT-PT maps IPv6 addresses to IPv4 addresses. If IPv6 is used on the inside of a network and IPv4 is used on the outside, a NAT-PT device receives IPv6 traffic on its inside interface and replaces the IPv6 header with an IPv4 header before sending it to an outside interface. Reply traffic follows the mapping backwards, enabling two-way communication.