IPv6 Configuration

In IPv4 there are public addresses, where in IPv6 there are global unicast addresses which can trasfer data quicker and are fully hierarchichal, fully routable and can be aggregated. In IPv4 there are also private IP adresses, where in IPv6 there are local addresses which are divided into link local addresses which is very narrow in scope, therefore local to a physical address and site local addresses which are wider in scope and is equivalent to the local address in IPv4, used to access local network but not the public network. Besides unicasts, there are also multicast addresses which starts with the prefix (FF00::/8). There is also anycasts addresses which are assigned to multiple interfaces, and an anycast packet is delivered to only ONE member, which is the closest member in an anycast group that shares the anycast address. The closest member is the first one that was learned by the router on a LAN, and the routing protocol metric on a WAN.

Site Level Aggregator in IPv6 is used to aggregate routes or subnetting in IPv4, but there are more routes in SLA then in IPv4 subnetting. It is 16 bits long and supports over 65.000 subnets.

Autoconfiguration in IPv6 is almost the same as DHCP configuration. There are 2 types of autoconfiguration which are stateless and stateful configuration. Stateful autoconfiguration is also known as DHCPv6 which has the same concepts as DHCP. The host will request an IP address to the server and obtain an information from it. With stateless autoconfiguration the (Duplicate Address Detection) DAD procedure will be executed where the host will configure its own link-local address using FE80:: followed by the MAC address of the host. After configuring its initial IPv6 configuration it will send an Neighbor Solicitation (NS) message to the multicast address FF02::1 (all host multicast address) to check out whether there is another host using the same address. If there is another host using that address (which is supposed not to happen, because each MAC address is unique) the other host will send an Neighbor Advertisement message and the host will disable its MAC address. If this does not happen, than the address is valid and it will send and Router Solicitation (RS) message to the all router multicast address which is FF02::2 to ask the router for other configuration such as the network prefix. The router will send an Router Advertisement to the host and the IPv6 address of the host is complete.

There are also routing protocols in IPv6 some of them are RIP for IPv6/RIPng (new generation), EIGRP for IPv6, ISIS for IPv6, OSPFv3, Multiprotocol BGP/MGBPv4. However, there is no IGRP is not covered in IPv6. To enable Cisco’s router IPv6 routing capabilities use the command config#ipv6 unicast-routing.

For OSPFv3, the process is enable per interfaceas opposed to global configuration in OSPFv2. To enable it on an interface use the command (config-if)#ipv6 ospf area . To create a router ID if there is none, use the command (config-router)#router-id . Other notes for OSPFv3 is that OSPFv3 NBMA configuration still needs neighbor statements and point-to-point and point-to-multipoint configurations do not elect DR and BDR such as in IPv4. OSPFv3 allows a link to be a part of multiple instances, whereas in IPv4 to only 1 instance. OSPFv3 headers are smaller because they have no authentication fields. The OSPF reserved address 224.0.0.5 in IPv6 is FF02::5 and 224.0.0.6 in IPv6 is FF02::6.

Basic configuration to create an adjecency on the routers using ospf is to configure the following on the adjacent routers:

(config)#ipv6 unicast-routing

(config)#ipv6 cef

(config)#ipv6 router ospf 1

(config-rtr)#router-id

(config)#int

(config-if)#ipv6 ospf area

To verify, the following commands can be used:

#show ipv6 ospf neighbor or #show ipv6 ospf neighbor detail

#show ipv6 ospf interface or #show ipv6 ospf interface

To clear/reset the configuration use the command #clear ipv6 ospf process

There are 3 known ways to migrate from IPv4 to IPv6 which are dual stack, 6-4 tunnel and NAT PT (Network Address Translation – Protocol Translation). With dual stack, an interface has 2 IP addresses which are IPv4 address and IPv6 address. With a 6-4 tunnel, an IPv6 packet is encapsulated to an IPv4 packet and sent through the IPv4 network. When it reaches the end, it will decapsulate the packet and sent through the IPv6 network again using the original IPv6 address. This is a scalable and easy solution, and the network will be torn down if the session ends.The edge routers will have a unique address which is 2002:IPv4 address of the router in hex ::/48 prefix. NAT PT work similar to original NAT, except that NAT PT routers translate IPv4 addresses to IPv6 addresses and in reverse.

To create a tunnel use the command:

(config)#int

(config-if)#ip address

(config-if)#int tunnel

(config-if)#ipv6 address 2002:HHHH:HHHH::/48

-- 13 April 2011 --