CST3607 Class Notes 2021-12-09

News & Tools

Three strategies for the transition from IPv4 to IPv6

  • Dual Stack
  • Tunneling
    • A strategy used when two computers using IPv6 want to communicate with each other and the packet must pass through a region that uses IPv4.
    • The IPv6 packet is encapsulated within an IPv4 packet
    • The IPv4 packet carries an IPv6 packet as data/payload, and the protocol value is set to 41
  • Header Translation
    • The header of the IPv6 packet is converted to an IPv4 header
    • Used when a host wants to use IPv6, but the receiver does not understand/support IPv6

Advantages that IPv6 has over IPv4.

  • Larger address space. (This is the primary reason that IPv6 was developed.)
  • Better header format
  • New options
  • Allowance for extension
  • Support for resource allocation
  • Support for more security

IPv6 Addressing

  • IPv6 Tutorial [9tut.com]
  • Mastering IPv6 SLAAC Concepts and Configuration [ciscopress.com]
  • What is the problem with StateLess Automatic Address Configuration (SLAAC)?
    • With SLAAC, by default no DNS configuration is returned to the host.
  • IPv4/IPv6 subnet calculator
  • IPv6 addresses fall into one of three categories / transmission methods
    • Unicast
    • Multicast
    • Anycast addressing routes datagrams to a single member of a group of potential receivers that are all identified by the same destination address. This is a one-to-one-of-many association.
  • There are no broadcast addresses in IPv6.
  • Types of IPv6 addresses.
    • Link-local addresses are similar to APIPA addresses and start with FE80.
      • A link-local address is a network address that is valid only for communications within the network segment or the broadcast domain that the host is connected to.
      • Link-local addresses are not guaranteed to be unique beyond their network segment, therefore routers do not forward packets with link-local addresses.
      • Link-local addresses are most often assigned automatically through a process known as stateless address autoconfiguration or link-local address autoconfiguration.
    • Unique local addresses are similar to private IP addresses and start with FC00.
      • Unique local addresses may be used freely, without centralized registration, inside a single site or organization or spanning a limited number of sites or organizations.
      • They are routable only within the scope of such private networks, but not in the global IPv6 Internet.
    • Global addresses are like public IP addresses and start with 2000.
    • The IPv6 loopback address is ::1.

Global Unicast IPv6 Address

Global Routing Prefix

  • This is assigned by the ISP to a customer or site.
  • The Global Routing Prefix is determined by the prefix-length notation. (example /48 or /64).
  • This is similar to the network portion of an IPv4 address.

Subnet ID

  • This is similar to the subnet portion of an IPv4 address.
  • The difference is in IPv4 the subnet is borrowed from the host portion of the address.
  • In IPv6 the Subnet ID is a separate field (/48 to /64) and not necessarily part of the Interface ID.

Interface ID

  • The Interface ID uniquely identifies an interface on the local subnet.

IPv6 Address Format

IPv6 Address Format: x:x:x:x:x:x:x:x ? where x is a 16 bit hexadecimal field, and x represents four hexadecimal digits.

An example IPv6 Address: 2001:0000:5723:0000:0000:D14E:DBCA:0764

There are:

  • 8 groups of 4 hexadecimal digits, with each group separated by a colon. “:”
  • Each group represents 16 bits (4 hexadecimal digits * 4 bits)
  • Each hexadecimal digit is equal to 4 bits
  • Each pair of hexadecimal digits are equal to 8 bits = 1 byte.
  • Hex digits are not case sensitive, so “DBCA” is same as “dbca” or “DBca”?
  • Each group is referred to as a “hextet”

IPv6 (128-bit) address contains two parts:

  • The first 64-bits is known as the prefix. The prefix includes the network and subnet address. Because addresses are allocated based on physical location, the prefix also includes global routing information. The 64-bit prefix is often referred to as the global routing prefix.
  • The last 64-bits is the interface ID. This is the unique address assigned to an interface.

Note: Addresses are assigned to interfaces (network connections), not to the host. Each interface can have more than one IPv6 address.

IPv6: Zero Omission Rules

  • Rule 1: Omission of the Leading 0s:
    • Rule 1 allows you to remove all the leading 0s in each individual hextet.
  • Rule 2: Omission of the All-0 Hextets:
    • Rule 2 uses a double colon :: to represent a single “contiguous” set of all zero hextexts.
    • It can only be used once within an IPv6 address.


  • In OSPFv3, the interfaces and therefore the networks attached to them can be configured directly on the interface, in interface configuration mode.
  • This is because if we go with the interface configuration option, the router configuration process is added automatically.
    • Router1(config-if)# ipv6 ospf 10 area 0

What is the command to configure OSPFv3 on a router?

  • In global configuration mode?
  • In interface configuration mode?


  • Internet Control Message Protocol version 6 (ICMPv6) is the implementation of the Internet Control Message Protocol (ICMP) for Internet Protocol version 6 (IPv6).
  • ICMPv6 is defined in RFC 4443. ICMPv6 is an integral part of IPv6 and performs error reporting and diagnostic functions (e.g., ping)

Stateless Autoconfiguration (EUI-64)

SLAAC (State Less Automatic Address Configuration):

Stateless Autoconfiguration is a useful solution because it allows devices on a network to address themselves with a link-local unicast address as well as with a global unicast address. This process happens through first learning the prefix information from the router and then appending the device’s own interface address as the interface ID.

To perform auto-configuration, a host goes through a basic two-step process:

  1. First, the host needs the prefix information, similar to the network portion of an IPv4 address, to configure its interface, so it sends a router solicitation (RS)request for it. This RS is then sent out as a multicast to all routers (FF02::2). The RS message is ICMP type 133.
  2. The router answers back with the required prefix information via a router advertisement (RA). An RA message also happens to be a multicast packet that’s sent to the all-nodes multicast address (FF02::1) and is ICMP type 134. RA messages are sent on a periodic basis, but the host sends the RS for an immediate response so it doesn’t have to wait until the next scheduled RA to get what it needs.

What is the problem with StateLess Automatic Address Configuration (SLAAC)?

  • With SLAAC, by default, no DNS configuration is returned to the host.

DHCPv6 (Stateful) (IP and Options)

– Static
– Stateful DHCP (IP and Options)
– Stateless DHCP (no IP, just Options) [DNS, Domain you belong to.] (Used with SLAAC)



Assignment #6: IPv6 Zero Omission Rules


Read / Watch / Do

CCNA Certification Study Guide, Volume 2

  • Read Chapter 18 : Troubleshooting IP
  • Do the Written Labs
  • Answer the Review Questions
    • Do not submit your answers for this chapter. The answers are in Appendix.

Study for the Final Exam

Better Focus and Efficient Studying When Not Multitasking