Configure IPv6 Address on Cisco Routers

IP version 6 (IPv6) is a new version of the Internet Protocol (IP), intended to replace the older IPv4 which is still employed on the vast majority of Internet hosts. IPv6 increases the IP address size from 32 bits to 128 bits to support a much greater number of addressable hosts. IPv4 can support 2³² = 4,294,967,296 or over four billion unique addresses but this address space has almost exhausted due to immense expansion in the size of the Internet over the years. IPv6 on the other hand can support 2¹²⁸ = 3.4 * 10³⁸ addresses, a number so large that it would solve the scarcity of IP address space once and for ever.

IPv6 conventions write the 128 bit IPv6 address as 8 quartets of hex digits, separated by colons, for example:

2001:2222:BBBB:0003:1234:5678:9ABC:0012

As you can see, IPv6 addresses are lengthy even in hexadecimal. Two conventions are used to shorten what must be typed for an IPv6 address:

• Omit the leading 0s in any given quartet. However you must leave at least one number in any quartet.
• Represent consecutive quartets of all 0s with double colon (or :: ) but only for one such occurrence in a given address.

In order to see these conventions in action, consider the following IPv6 address:

FE00:0000:0000:0000:0012:0000:0000:0043

The leftmost consecutive quartets of all 0s can be represented with double colon (::). Even if we have more consecutive zeros later on, only one time is allowed to have the double colon notation in the IP. So we have the following valid abbreviation for the above IPv6 address.

FE00::12:0:0:43

There are three general types of IPv6 addresses: unicast, multicast, and anycast. There are further categories in unicast addresses one of which is IPv6 global unicast addresses. An IPv6 global unicast address is similar to a public IP address in IPv4, that is, an IP address that can be routed across the public Internet.

Figure 1 – IPv6 Global Unicast Address

There are two options for static configuration of IPv6 addresses on Cisco routers. For one option, you configure the entire 128-bit IPv6 address, and for the other, you just configure the 64-bit prefix and tell the device to use an EUI-64 calculation for the interface ID portion of the address. Extended Unique Identifier or EUI-64 format allows a host to automatically assign itself a unique 64-bit IPv6 interface identifier without manual configuration. Both options result in the router interface learning its full 128-bit IPv6 address and prefix-length, one way or the other.

Let’s now configure IPv6 addresses for the network shown in Figure 2. The figure shows two IPv6 subnet numbers with the two links.

Figure 2 – IPv6 Configuration

Let’s first configure interfaces Fa0/0 and S0/0 of R1:

R1>enable
R1#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#interface FastEthernet0/0
R1(config-if)#ipv6 address 2000:0:0:D::/64 eui-64
R1(config-if)#interface Serial0/0
R1(config-if)#ipv6 address 2000:0:0:C::1/64
R1(config-if)#end

Let’s now verify if IPv6 addresses have been correctly configured using commands show ipv6 interface brief and show ipv6 interface as show below.

R1#show ipv6 interface brief
FastEthernet0/0            [up/up]
FE80::C000:17FF:FE7C:0
2000::D:C000:17FF:FE7C:0
Serial0/0                  [up/up]
FE80::C000:17FF:FE7C:0
2000:0:0:C::1

R1#show ipv6 interface FastEthernet0/0
FastEthernet0/0 is up, line protocol is up
IPv6 is enabled, link-local address is FE80::C000:17FF:FE7C:0
No Virtual link-local address(es):
Global unicast address(es):
2000::D:C000:17FF:FE7C:0, subnet is 2000:0:0:D::/64 [EUI]
Joined group address(es):
FF02::1
FF02::1:FF7C:0
MTU is 1500 bytes
ICMP error messages limited to one every 100 milliseconds
ICMP redirects are enabled
ICMP unreachables are sent
ND DAD is enabled, number of DAD attempts: 1
ND reachable time is 30000 milliseconds

Let’s now proceed to configure IPv6 addresses on R2 and R3 as well.

R2>enable
R2#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)#interface Serial0/0
R2(config-if)#ipv6 address 2000:0:0:C::2/64
R2(config-if)#end
R2#

R3>enable
R3#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
R3(config)#interface FastEthernet0/0
R3(config-if)#ipv6 address 2000:0:0:D::/64 eui-64
R3(config-if)#end
R3#

Let’s now go back to R1 and verify if we can ping the IPv6 address 2000:0:0:C::2 on interface S0/0 of R2.

R1#ping 2000:0:0:C::2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2000:0:0:C::2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 0/8/28 ms

Reference from http://www.networkstraining.com

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