Cisco IPv4 and IPv6 Address Management – Cisco Zero-Touch Network Provisioning

5 Jul, 2024 Liam Brooks

IPv6 Address Size (10.3.2)–Cisco IPv4 and IPv6 Address Management

IPv6 addressing will eventually replace IPv4 addressing although both types of addresses will coexist for the foreseeable future. IPv6 overcomes the limitations of IPv4 and has features that better suit current and foreseeable network demands. The 32-bit IPv4 address space provides approximately 4,294,967,296 unique addresses.

IPv6 address space provides 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses, or 340 undecillion addresses, which is roughly equivalent to the number of grains of sand on Earth. Table 10-1 provides a visual to compare the IPv4 and IPv6 address space.

Table 10-1 Number of Zeros for Increasing Levels of Scientific Notation

Number Name	Scientific Notation	Number of Zeros
1 Thousand	10 3	1,000
1 Million	10 6	1,000,000
1 Billion	10 9	1,000,000,000
1 Trillion	10 12	1,000,000,000,000
1 Quadrillion	10 15	1,000,000,000,000,000
1 Quintillion	10 18	1,000,000,000,000,000,000
1 Sextillion	10 21	1,000,000,000,000,000,000,000
1 Septillion	10 24	1,000,000,000,000,000,000,000,000
1 Octillion	10 27	1,000,000,000,000,000,000,000,000,000
1 Nonillion	10 30	1,000,000,000,000,000,000,000,000,000,000
1 Decillion	10 33	1,000,000,000,000,000,000,000,000,000,000,000
1 Undecillion	10 36	1,000,000,000,000,000,000,000,000,000,000,000,000

The following are other benefits of the IPv6 protocol:

There is no need for NAT. Each device can have its own globally routable address.
Autoconfiguration capabilities simplify address administration.

The designers of IPv6 thought that it would be adopted quickly, as the number of remaining available IPv4 address blocks was decreasing rapidly. Initial estimates were that IPv6 would be globally deployed by 2003. Obviously, these estimates were incorrect.

Video—Compare IPv4 and IPv6 Addressing (10.3.3)

Refer to the online course to view this video.

IPv4 and IPv6 Coexistence (10.3.4)

There is no specific date to move to IPv6. Both IPv4 and IPv6 will coexist in the near future, and the transition is taking several years. The IETF has created various protocols and tools to help network administrators migrate their networks to IPv6. The migration techniques can be divided into three categories: dual stack, tunneling, and translation.

Dual Stack

Dual stack enables IPv4 and IPv6 to coexist on the same network segment, as shown in Figure 10-6. Dual stack devices run both IPv4 and IPv6 protocol stacks simultaneously. Known as native IPv6, this means the customer network has an IPv6 connection to its ISP and is able to access content found on the Internet over IPv6.

Figure 10-6 A Dual Stack Topology

Tunneling

Tunneling is a method of transporting an IPv6 packet over an IPv4 network, as shown in Figure 10-7. The IPv6 packet is encapsulated inside an IPv4 packet, similar to other types of data.

Figure 10-7 Routing IPv6 Packets Inside an IPv4 Tunnel

Translation

Network Address Translation 64 (NAT64) enables IPv6-enabled devices to communicate with IPv4-enabled devices using a translation technique similar to NAT for IPv4. An IPv6 packet is translated to an IPv4 packet, and an IPv4 packet is translated to an IPv6 packet. The NAT64 router translates the different IP addresses between networks (the solid line) so that the PCs with different IP addresses can communicate (the dotted line), as shown in Figure 10-8.

Figure 10-8 Translation Between IPv4 and IPv6

IPv6 Features (10.4)

IPv6 is more than just larger address space. A new IP protocol was an opportunity to make performance improvements and provide much-needed new features.

Video—The Hexadecimal Number System (10.4.1)

Refer to the online course to view this video.

Video—Differences Between IPV4 and IPv6 (10.4.2)

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IPv6 Autoconfiguration and Link-Local Addresses (10.4.3)

In addition to the increase in length, IPv6 addresses have other characteristics that are different than IPv4 addresses. Among the differences are the following:

Address autoconfiguration—Stateless Address Autoconfiguration (SLAAC) allows a host to create its own Internet-routable address (global unicast address, or GUA) without the need for a DHCP server. As shown in Figure 10-9, with the default method, the host receives the prefix (network address), prefix length (subnet mask), and default gateway from the Router Advertisement message of the router. The host can then create its own unique interface ID (host portion of the address) to give itself a routable global unicast address.

Figure 10-9 SLAAC Operation

Link-local address—A link-local address is used when communicating with a device on the same network.

The developers of IPv6 made improvements to IP and related protocols such as ICMPv6. These improvements include features related to efficiency, scalability, mobility, and flexibility for future enhancements.

Video—IPv6 Address Representation (10.4.4)

Refer to the online course to view this video.

5 May, 2024 Liam Brooks

Objectives–Cisco IPv4 and IPv6 Address Management

Upon completion of this chapter, you will be able to meet the following objectives:

Describe network boundaries.
Explain the purpose of Network Address Translation in small networks.
Explain why IPv6 addressing will replace IPv4 addressing.
Explain features of IPv6.

Key Terms

This chapter uses the following key terms. You can find the definitions in the Glossary.

dual stack page 201

Internet of Things (IoT) page 200

IPv6 address page 200

link-local address page 204

Network Address Translation (NAT) page 197

Network Address Translation 64 (NAT64) page 203

Regional Internet Registries (RIRs) page 199

Stateless Address Autoconfiguration (SLAAC) page 203

tunneling page 202

Introduction (10.0.1)

So far, we‛ve talked only about the existence of IPv4 addressing. This chapter explains how IPv4 and IPv6 will coexist in networks for some time to come. It shows you how an IPv6 address is structured and the benefits of IPv6 addressing over IPv4. But the fun part of this chapter is converting binary to hexadecimal notation. Don‛t know what hexadecimal notation is? Read on.

Network Boundaries (10.1)

Routers connect one network to another network. Only devices on separate networks need to forward their packets to a router to be able to communicate.

Video—Gateways to Other Networks (10.1.1)

Refer to the online course to view this video.

Routers as Gateways (10.1.2)

The router provides a gateway through which hosts on one network can communicate with hosts on other networks. Each interface on a router is connected to a separate network.

The IPv4 address assigned to the interface identifies which local network is connected directly to it.

Every host on a network must use the router as a gateway to other networks. Therefore, each host must know the IPv4 address of the router interface connected to the network where the host is attached. This address is known as the default gateway address. It can be either statically configured on the host or received dynamically by DHCP.

When a wireless router is configured to be a DHCP server for the local network, it automatically sends the correct interface IPv4 address to the hosts as the default gateway address. In this manner, all hosts on the network can use that IPv4 address to forward messages to hosts located at the ISP and get access to hosts on the Internet. Wireless routers are usually set to be DHCP servers by default.

The IPv4 address of that local router interface becomes the default gateway address for the host configuration. The default gateway is provided, either statically or by DHCP.

When a wireless router is configured as a DHCP server, it provides its own internal IPv4 address as the default gateway to DHCP clients. It also provides them with their respective IPv4 address and subnet mask, as shown in Figure 10-1.

Figure 10-1 A Router Serving as a Default Gateway

Routers as Boundaries Between Networks (10.1.3)

The wireless router acts as a DHCP server for all local hosts attached to it, either by Ethernet cable or wirelessly. These local hosts are referred to as being located on an internal, or inside, network. Most DHCP servers are configured to assign private addresses to the hosts on the internal network rather than Internet routable public addresses. This configuration ensures that, by default, the internal network is not directly accessible from the Internet.

The default IPv4 address configured on the local wireless router interface is usually the first host address on that network. Internal hosts must be assigned addresses within the same network as the wireless router, either statically configured, or through DHCP. When configured as a DHCP server, the wireless router provides addresses in this range. It also provides the subnet mask information and its own interface IPv4 address as the default gateway, as shown in Figure 10-2.

Figure 10-2 Default Router as Both a DHCP Server and a DHCP Client

Many ISPs also use DHCP servers to provide IPv4 addresses to the Internet side of the wireless router installed at their customer sites. The network assigned to the Internet side of the wireless router is referred to as the external, or outside, network.

When a wireless router is connected to the ISP, it acts like a DHCP client to receive the correct external network IPv4 address for the Internet interface. ISPs usually provide an Internet-routable address, which enables hosts connected to the wireless router to have access to the Internet.

The wireless router serves as the boundary between the local internal network and the external Internet.

5 Jul, 2023 Liam Brooks

Objectives–Cisco Dynamic Addressing with DHCP

Upon completion of this chapter, you will be able to complete the following objectives:

Compare static and dynamic IPv4 addressing.
Configure a DHCPv4 server to dynamically assign IPv4 addresses.

Key Term

This chapter uses the following key term. You can find the definition in the Glossary.

Dynamic Host Configuration Protocol (DHCP) page 183

Introduction (9.0.1)

Let‛s say you have three computers, a networked printer, and a wireless router. That‛s just a handful of devices that need an IP address, which you can assign yourself. But what if you had 100 computers. It might take more than a few hours to assign IP addresses and to verify connectivity for all of them. If you have an ISP, you can handle this task dynamically with DHCP. In fact, you can use DHCP to dynamically assign IP addresses to your devices in any network, including a small home network. This is definitely worth learning about.

Static and Dynamic Addressing (9.1)

It is important that devices have the correct IPv4 addressing information. This information includes the IPv4 address, subnet mask, default gateway address, and DNS server address.

Static IPv4 Address Assignment (9.1.1)

IPv4 addresses can be assigned either statically or dynamically.

With a static assignment, the network administrator must manually configure the network information for a host. At a minimum, this configuration includes the host IPv4 address, subnet mask, and default gateway, as shown in Figure 9-1.

Figure 9-1 Static IPv4 Addressing on a Windows PC

Static addresses have some advantages. For instance, they are useful for printers, servers, and other networking devices that need to be accessible to clients on the network. If hosts normally access a server at a particular IPv4 address, it would not be good if that address changed.

Static assignment of addressing information can provide increased control of network resources, but entering the information on each host can be time consuming. When IPv4 addresses are entered statically, the host only performs basic error checks on the IPv4 address. Therefore, errors are more likely to occur.

When static IPv4 addressing is used, it is important to maintain an accurate list of which IPv4 addresses are assigned to which devices. Additionally, these are permanent addresses and are not normally reused.

Dynamic IPv4 Address Assignment (9.1.2)

On local networks it is often the case that the user population changes frequently. New users arrive with laptops and need a connection. Others have new workstations that need to be connected. Rather than have the network administrator assign IPv4 addresses for each workstation, it is easier to have IPv4 addresses assigned automatically. This is done using a protocol known as Dynamic Host Configuration Protocol (DHCP).

DHCP automatically assigns addressing information such as IPv4 address, subnet mask, default gateway, and other configuration information, as shown in Figure 9-2.

Figure 9-2 Dynamic IPv4 Addressing on a Windows PC

DHCP is generally the preferred method of assigning IPv4 addresses to hosts on large networks because it reduces the burden on network support staff and virtually eliminates entry errors.

Another benefit of DHCP is that an address is not permanently assigned to a host but is only leased for a period of time. If the host is powered down or taken off the network, the address is returned to the pool for reuse. This is especially helpful with mobile users who come and go on a network.

5 Jul, 2021 Liam Brooks

Create a LAN (7.3)–Cisco Routing Between Networks Layer

End devices, both clients and servers, are connected to LANs. The LAN is how users access the network and reach other networks.

Local-Area Networks (7.3.1)

The term local-area network (LAN) refers to a local network or a group of interconnected local networks that are under the same administrative control, as shown in Figure 7-11. In the early days of networking, LANs were defined as small networks that existed in a single physical location. Although LANs can be a single local network installed in a home or small office, the definition of LAN has evolved to include interconnected local networks consisting of many hundreds of hosts, installed in multiple buildings and locations.

Figure 7-11 Collection of Local Networks Under the Same Administrative Control

The important thing to remember is that all the local networks within a LAN are under one administrative control. Other common characteristics of LANs are that they typically use Ethernet or wireless protocols, and they support high data rates.

The term intranet is often used to refer to a private LAN that belongs to an organization and is designed to be accessible only by the members of the organization, employees, or others with authorization.

Local and Remote Network Segments (7.3.2)

Within a LAN, it is possible to place all hosts on a single local network or divide them between multiple networks connected by a distribution layer device. How this placement is determined depends on the desired results.

All Hosts in One Local Segment

Placing all hosts on a single local network allows them to be seen by all other hosts, as shown in Figure 7-12. The reason is that there is one broadcast domain and hosts use ARP to find each other.

Figure 7-12 A Local Segment

In a simple network design, it may be beneficial to keep all hosts within a single local network. However, as networks grow in size, increased traffic decreases network performance and speed. In this case, it may be beneficial to move some hosts onto a remote network.

Advantages of a single local segment:

Appropriate for simple networks
Less complexity and lower network administrative cost
The capability of devices to be “seen” by other devices
Faster data transfer—more direct communication
Ease of device access

Disadvantages of a single local segment:

All hosts are in one broadcast domain, which causes more traffic on the segment and may slow network performance.
Implementing quality of service (QoS) is harder; QoS gives priority to certain types of messages during times of network congestion.
Implementing security is harder.

Hosts on a Remote Segment

Placing additional hosts on a remote network decreases the impact of traffic demands, as shown in Figure 7-13. However, hosts on one network are not able to communicate with hosts on the other without the use of routing. Routers increase the complexity of the network configuration and can introduce latency, or time delay, on packets sent from one local network to the other.

Figure 7-13 Router Segmenting the Local Network

Advantages:

Is more appropriate for larger, more complex networks
Splits up broadcast domains and decreases traffic
Can improve performance on each segment
Makes the devices invisible to those on other local network segments
Can provide increased security
Can improve network organization

Disadvantages:

The use of routing is required (at the distribution layer).
The router can slow traffic between segments.
It is more complex and expensive (because a router is required).

Packet Tracer—Observe Data Flow in a LAN (7.3.3)

In this activity, you will complete the following objectives:

Develop an understanding of the basic functions of Packet Tracer.
Create/model a simple Ethernet network using three hosts and a switch.
Observe traffic behavior on the network.
Observe data flow of ARP broadcasts and pings.

Lab—Connect to a Wireless Router (7.3.4)

In this lab, you will complete the following objectives:

Connect a PC to a wireless router using an Ethernet cable.
Configure the PC with an appropriate IP address.
Verify the PC configuration using a command prompt.

Summary (7.4)

The following is a summary of each topic in the chapter:

The Need for Routing—As networks grow, you may need to divide one access layer network into multiple access layer networks. The distribution layer connects these independent local networks and controls the traffic flowing between them. It is responsible for ensuring that traffic between hosts on the local network stays local. Networking devices that make up the distribution layer are designed to interconnect networks, not individual hosts.

Devices that are beyond the local network segment are known as remote hosts. When a source device sends a packet to a remote destination device, routing is needed. Routing is the process of identifying the path to a destination. A router is a networking device that connects multiple Layer 3 IP networks. At the distribution layer of the network, routers direct traffic and perform other functions critical to efficient network operation. Routers, like switches, are able to decode and read the messages that are sent to them. Unlike switches, which make their forwarding decision based on the Layer 2 MAC address, routers make their forwarding decision based on the destination Layer 3 IP address.

The Routing Table—Each port, or interface, on a router connects to a different local network. Every router contains a table of all locally connected networks and the interfaces that connect to them. These routing tables can also contain information about the routes that the router uses to reach other remote networks. A router forwards a packet to one of two places: a directly connected network containing the destination host or to another router on the path to reach the destination host. When a router encapsulates the frame to forward it out of an Ethernet interface, it must include a destination MAC address. This is the MAC address of the destination host, if the destination host is part of a network locally connected to the router. If the router must forward the packet to another router through an Ethernet interface, it uses the MAC address of the connected router. Routers obtain these MAC addresses from ARP tables.

Routing tables contain the addresses of networks and the path to reach those networks. Entries can be made to the routing table in two ways: dynamically updated by information received from other routers in the network or manually entered by a network administrator.

How does the source host determine the MAC address of the router? A host is given the IPv4 address of the router through the default gateway address configured in its TCP/IP settings. The default gateway address is the address of the router interface connected to the same local network as the source host.

Create a LAN—The LAN refers to a local network or a group of interconnected local networks that are under the same administrative control. Other common characteristics of LANs are that they typically use Ethernet or wireless protocols, and they support high data rates.

In a simple network design, it may be beneficial to keep all hosts within a single local network. Placing some hosts on a remote network decreases the impact of traffic demands. However, hosts on one network are not able to communicate with hosts on the other without the use of routing.