IPv6 Addressing Scheme in Cisco Router

Before knowing IPv6 addressing we need to know why there is a need for IPv6 when we have IPv4.

IPv4 IP stands for Internet Protocol and v4 is version 4. IP addresses can be 32-bit integers in length expressed in decimal notation and provides 2^32 addresses.

Example: 192.168.2.1 could be an IPv4 address.

To read more about this, you can refer to the article What is IPv4?.

IPv6 stands for Internet Protocol version 6 these IP addresses can be 128-bit integers in length expressed in Hexadecimal notation and provides 2^128 addresses.

To read more about this, you can refer to the article What is IPv6?.

Why do we need an IPv6 address?

IPv6 is running out of addresses. IPv6 is the successor to IPv4 because IPv6 has a much larger 128-bit address space.
Internet Population- Increasing internet population and a limited address space of IPv4 issues with NAT and IoT, that’s why IPv6 is introduced because of larger addresses.

The Prefix of IPv6 Address:

The prefix length is represented as slash ‘/’ notation and is used to target the network part of an IPv6 address. The range is 0-128. The Recommended IPv6 prefix length for LANs and most other types of networks is about /64.

Types of IPv6 Unicast addresses:

As we know Ipv4 has only a single address where IPv6 addresses typically have two unicast addresses.

• Global unicast Address: This address type is equivalent to IPv4 addresses these are globally unique, internet-routable, and reachable addresses on the internet.
• Link-Local Address: Auto-configured IPv6 address is known as a Link-Local address. These addresses are a must for every IPv6-enabled device and are used to communicate with other devices on the same local link.

IPv6 (GUA):

IPv6 (GUA) are globally unique and routable on the IPv6 internet.

•  Only GUA’s with the first three bits of 001 or 2000::/3 are being assigned.
•  Available GUA’s start with a decimal 2 or 3.

1. Global routing prefix: global routing prefix is the portion of the address that is assigned by the provider such as an ISP to a customer or site. The most significant 48-bits are assigned as a Global routing prefix which is assigned to a specific. autonomous system

2. Subnet ID: The subnet ID is the portion between the global routing prefix and the interface ID.

3. Interface ID: The Interface ID is equal to the host part of an IPv4 address, It is must recommend that in most cases /64 subnets must be used which creates a 64-bit ID.

LLA: Link-Local Address

An IPv6 address enables a device to communicate with a distinct IPv6-enabled device on the equal link and fine on that link.

• Packets with a delivery or holiday spot LLA can’t be routed.
• Every IPv6-enabled network interface should have an LLA.
• If an LLA isn’t always configured manually on an interface the device will robotically create one.

Steps to Implement IPv6 Addressing Scheme in Cisco Router:

Device	Interface	IPv6 address	Link-Local Address
R1	G0/0	2001:db8:acad:1::1/64	fe80::1
	G0/1	2001:db8:acad:2::1/64	fe80::1
	S0/0/0	2001:db8:acad:3::1/64	fe80::1
R2	G0/0	2001:db8:acad:ca::1/64	fe80::2
	G0/1	2001:db8:acad:cc::1/64	fe80::2
	S0/0/0	2001:db8:acad:bc::1/64	fe80::2

Step 1: Assign the first IP address in the subnet to the router LAN interfaces.

we will configure the first router for that go to the Command-line interface of router 1 for interface G0/0.

 R1>en
 R1#conf t
 R1(config)#int G0/0
 R1(config-if)#ipv
 R1(config-if)#ipv6 ad
 R1(config-if)#ipv6 address 2001:db8:acad:1::1/64
 R1(config-if)#ipv6 ad
 R1(config-if)#ipv6 address fe80::1 link 
 R1(config-if)#ipv6 address fe80::1 link-local
 R1(config-if)#no shut  

Step 2: Now we’ll configure for interface G0/1.

R1(config)#int G0/1
R1(config-if)#ipv
R1(config-if)#ipv6 ad
R1(config-if)#ipv6 address 2001:db8:acad:2::1/64
R1(config-if)#ipv6 ad
R1(config-if)#ipv6 address fe80::1 link 
R1(config-if)#ipv6 address fe80::1 link-local
R1(config-if)#no shut  

Step 3: Now assign ipv6 for serial interface S0/0/0.

R1(config)#int S0/0/0
R1(config-if)#ipv
R1(config-if)#ipv6 ad
R1(config-if)#ipv6 address 2001:db8:acad:3::1/64
R1(config-if)#ipv6 ad
R1(config-if)#ipv6 address fe80::1 link 
R1(config-if)#ipv6 address fe80::1 link-local
R1(config-if)#no shut  

Step 4: then, we’ll assign addresses to Router 2 interfaces. So first let’s configure interface G0/0

 R2>en
 R2#conf t
 R2(config)#int G0/0
 R2(config-if)#ipv
 R2(config-if)#ipv6 ad
 R2(config-if)#ipv6 address 2001:db8:acad:ca::1/64
 R2(config-if)#ipv6 ad
 R2(config-if)#ipv6 address fe80::2 link 
 R2(config-if)#ipv6 address fe80::2 link-local
 R2(config-if)#no shut 

Step 5: Configure the interface G0/1

 R2(config)#int G0/1
 R2(config-if)#ipv
 R2(config-if)#ipv6 ad
 R2(config-if)#ipv6 address 2001:db8:acad:cc::1/64
 R2(config-if)#ipv6 ad
 R2(config-if)#ipv6 address fe80::2 link 
 R2(config-if)#ipv6 address fe80::2 link-local
 R2(config-if)#no shut 

Step 6: Now assign ipv6 for serial interface S0/0/0.Before Jumping into IPv6 addressing we need to know why there is a need for IPv6 when we have IPv4?

 R2(config)#int S0/0/0
 R2(config-if)#ipv
 R2(config-if)#ipv6 ad
 R2(config-if)#ipv6 address 2001:db8:bc:00cf::2/64
 R2(config-if)#ipv6 ad
 R2(config-if)#ipv6 address fe80::2 link 
 R2(config-if)#ipv6 address fe80::2 link-local
 R2(config-if)#no shut