Chapter 7: IP Addressing

Chapter 7: IP Addressing

1. IPv4 Addresses

   • Binary is a numbering system that consists of the numbers 0 and 1 called bits. In contrast, the decimal numbering system consists of 10 digits consisting of the numbers 0 – 9.

2. Positional Notation

   • Learning to convert binary to decimal requires an understanding of positional notation. Positional notation means that a digit represents different values depending on the “position” the digit occupies in the sequence of numbers.

3. Binary to Decimal Conversion

   • To convert a binary IPv4 address to its dotted decimal equivalent, divide the IPv4 address into four 8-bit octets. Next apply the binary positional value to the first octet binary number and calculate accordingly.

4. The Subnet Mask

   • IPv4 address
     • Unique IPv4 address of the host
   • Subnet mask
     • Used to identify the network/host portion of the IPv4 address
   • Default gateway
     • Identifies the local gateway (i.e. local router interface IPv4 address) to reach remote networks

5. IPv4 Communication

   • Unicast
     • The process of sending a packet from one host to an individual host as shown
   • Broadcast
     • The process of sending a packet from one host to all hosts in the network as shown
   • Multicast
     • The process of sending a packet from one host to a selected group of hosts, possibly in different networks, as shown

6. Public and Private IPv4 Addresses

   • Public IPv4 addresses are addresses which are globally routed between ISP (Internet Service Provider) routers. However, not all available IPv4 addresses can be used on the Internet.
     • Specifically, the private address blocks are
       • 10.0.0.0 /8 or 10.0.0.0 to 10.255.255.255
       • 172.16.0.0 /12 or 172.16.0.0 to 172.31.255.255
       • 192.168.0.0 /16 or 192.168.0.0 to 192.168.255.255

7. Special User IPv4 Addresses

   • There are certain addresses such as the network address and broadcast address that cannot be assigned to hosts.
     • Loopback addresses (127.0.0.0 /8 or 127.0.0.1 to 127.255.255.254)
       • More commonly identified as only 127.0.0.1, these are special addresses used by a host to direct traffic to itself.
     • Link-Local addresses (169.254.0.0 /16 or 169.254.0.1 to 169.254.255.254)
       • More commonly known as the Automatic Private IP Addressing (APIPA) addresses, they are used by a Windows DHCP client to self-configure in the event that there are no DHCP servers available.Useful in a peer-to-peer connection.
     • TEST-NET addresses (192.0.2.0/24 or 192.0.2.0 to 192.0.2.255)
       • These addresses are set aside for teaching and learning purposes and can be used in documentation and network examples.

8. Legacy Classful Addressing

   • Class A (0.0.0.0/8 to 127.0.0.0/8)
     • Designed to support extremely large networks with more than 16 million host addresses.
   • Class B (128.0.0.0 /16 – 191.255.0.0 /16)
     • Designed to support the needs of moderate to large size networks with up to approximately 65,000 host addresses. It used a fixed /16 prefix with the two high-order octets to indicate the network address and the remaining two octets for host addresses.

9. IPv4 and IPv6 Coexistence

   • There is not a single date to move to IPv6. For the foreseeable future, both IPv4 and IPv6 will coexist.
     • Dual Stack
       • As shown in Figure 1, dual stack allows IPv4 and IPv6 to coexist on the same network segment.
     • Tunneling
       • As shown in Figure 2, tunneling is a method of transporting an IPv6 packet over an IPv4 network.
     • Translation
       • As shown in Figure 3, Network Address Translation 64 (NAT64) allows IPv6-enabled devices to communicate with IPv4-enabled devices using a translation technique similar to NAT for IPv4.

10. IPv6 Address Types

    • There are three types of IPv6 addresses
      • Unicast
        • An IPv6 unicast address uniquely identifies an interface on an IPv6-enabled device.
      • Multicast
        • An IPv6 multicast address is used to send a single IPv6 packet to multiple destinations.
      • Anycast
        • An IPv6 anycast address is any IPv6 unicast address that can be assigned to multiple devices.

11. IPv6 Unicast Addresses

    • The most common types of IPv6 unicast addresses are global unicast addresses (GUA) and link-local unicast addresses.
      • Global unicast
        • A global unicast address is similar to a public IPv4 address.
      • Link-local
        • Link-local addresses are used to communicate with other devices on the same local link.
      • Unique local
        • Another type of unicast address is the unique local unicast address.

12. ICMPv4 and ICMPv6

    • Although IP is only a best-effort protocol, the TCP/IP suite does provide for messages to be sent in the event of certain errors.
      • ICMP messages common to both ICMPv4 and ICMPv6 include
        • Host confirmation
        • Destination or Service Unreachable
        • Time exceeded
        • Route redirection

13. Traceroute – Testing the Path

    • Ping is used to test connectivity between two hosts but does not provide information about the details of devices between the hosts.
      • Round Trip Time (RTT)
        • Using traceroute provides round trip time for each hop along the path and indicates if a hop fails to respond.
      • IPv4 TTL and IPv6 Hop Limit
        • Traceroute makes use of a function of the TTL field in IPv4 and the Hop Limit field in IPv6 in the Layer 3 headers, along with the ICMP time exceeded message.