Cisco Router Challenge 100

 

Outline

 

This challenge involves the configuring IPv6 on interfaces.The objectives of this challenge are to:

 

 

Commands

 

# config t

(config)# int e0

(config-if)# ipv6 address 2000:1111:1111:1::/64 eiu-64

 

Theory

 

The IP header (IP Ver4) is added to higher-level data (as defined in RFC791). This header  contains a 32-bit IP address of the destination node. Unfortunately, the standard 32-bit IP address is not large enough to support the growth in nodes connecting to the Internet. Thus a new standard, IP Version 6 (IP Ver6, aka, IP, The Next Generation, or IPng), has been developed to support a 128-bit address, as well as additional enhancements, such as authentication and data encryption.

The main techniques being investigated are:

 

·         TUBA (TCP and UDP with bigger addresses).

·         CATNIP (common architecture for the Internet). The main idea was to define a common packet format which was compatible with IP, CLNP (Connectionless Network Protocol) and IPX. CLNP was proposed by the OSI as a new protocol to replace IP, but it has never really been adopted (mainly because it was too inefficient).

·         SIPP (Simple Internet protocol plus). This scheme increases the number of address bits from 32 to 64, and gets rid of unused fields in the IP header.

 

It is likely that none of these will provide the complete standard and the resulting standard will be a mixture of the three. The RFC1883 specification outlines the main changes as:

 

·         Expanded addressing capabilities. The size of the IP address will be increased to 128 bits, rather than 32 bits. This will allow for more levels of addressing hierarchy, an increased number of addressable nodes and a simpler auto-configuration of addresses. With multicast routing, the scalability is improved by adding a scope field to the multicast addresses. As well as this, an anycast address has been added so that packets can be sent to any one of a group of nodes.

·         Improved IP header format. This tidies the IPv4 header fields by dropping the least used options, or making them optional.

·         Improved support for extensions and options. These allow for different encodings of the IP header options, and thus allow for variable lengths and increased flexibility for new options.

·         Flow labeling capability.  A new capability is added to enable the labeling of packet belonging to particular traffic flows for which the sender requests special handling, such as non-default quality of service or real-time service.

·         Authentication and privacy capabilities. Extensions to support authentication, data integrity, and (optional) data confidentiality are specified for IPv6.

Autoconfiguration and multiple IP addresses

IPv4 requires a significant amount of human intervention to set up the address of each of  the nodes. IPv6 improves this by supplying autoconfiguration renumbering facilities, which allows hosts to renumber without significant human intervention.

 

IPv4 has a stateful address structure, which either requires the user to manually set up the IP address of the computer or to use DHCP servers to provide IP addresses for a given MAC address. If a node moves from one subnet to another, the user must reconfigure the IP address, or request a new IP address from the DHCP. IPv6 supports a stateless autoconfiguration, where a host constructs its own IPv6. This occurs by adding its MAC address to a subnet prefix. The host automatically learns which subnet it is on by communicating from the router which is connected to the network that the host is connected to.

 

IPv6 supports multiple IP addresses for each host. These addresses can be either valid, deprecated or invalid. A valid address would be used for new and existing communications. A deprecated address could be used only for the existing communications (as they perhaps migrated to the new address). An invalid address would not be used for any communications. When renumbering, a host would deprecate the existing IP address, and set the new IP address as valid. All new communications would use the new IP address, but connections to the previous address would still operate. This allows a node to gradually migrate from one IP address to another.

IPv6 header format

Figure 1 shows the basic format of the IPv6 header. The main fields are:

 

·         Version number (4 bits) – contains the version number, such as 6 for IP Ver6. It is used to differentiate between IPv4 and IPv6.

·         Priority (4 bits) – indicates the priority of the datagram, and gives 16 levels of priority (0 to 15). The first eight values (0 to 7) are used where the source is providing congestion control (which is traffic that backs-off when congestion occurs), these are:

 

·       0 defines no priority.

·       1 defines background traffic (such as netnews).

·       2 defines unattended transfer (such as e-mail), 3 (reserved).

·       4 defines attended bulk transfer (FTP, NFS), 5 (reserved).

·       6 defines interactive traffic (such as telnet, X-windows).

·       7 defines control traffic (such as routing protocols, SNMP).

 

The other values are used for traffic that will not back off in response to congestion (such as real-time traffic). The lowest priority for this is 8 (traffic which is the most willing to be discarded) and the highest is 15 (traffic which is the least willing to be discarded).

 

·         Flow label (24 bits) – still experimental, but will be used to identify different data flow characteristics. It is assigned by the source and can be used to label data packets which require special handling by IPv6 routers, such as defined QoS (Quality of Service) or real-time services.

·         Payload length (16 bits) – defines the total size of the IP datagram (and includes the IP header attached data).

·         Next header – this field indicates which header follows the IP header (it uses the same IPv4). For example: 0 defines IP information; 1 defines ICMP information; 6 defines TCP information and 80 defines ISO-IP.

·         Hop limit – defines the maximum number of hops that the datagram takes as it traverses the network. Each router decrements the hop limit by 1; when it reaches 0 it is deleted. This has been renamed from IPv4, where it was called time-to-live, as it better describes the parameter.

·         IP addresses (128 bits) – defines IP address. There will be three main groups of IP addresses: unicast, multicast and anycast. A unicast address identifies a particular host, a multicast address enables the hosts within a particular group to receive the same packet, and the anycast address will be addressed to a number of interfaces on a single multicast address.

 

Figure 1   Ver6 header format

 

IPv6 has a simple header, which can be extended if required. These are:

 

·       Routing header.                               

·       Fragment header.

·       Authentication header.

·       Encrypted security payload.

·       Destinations options header.

 

IPv6 addresses do not use the dotted notion and are written in a hexadecimal format, such as:

 

114F: 0000: 0000: 0000: 0006: 0600: 4411: CB1D

 

Often the leading zero's are omitted to give:

 

114F: 0: 0: 0: 6: 600: 4411: CB1D

 

This address can be shorted further by converting all zero values to a double colon, to give:

 

114F::6:600:4411:CB1D

 

The unicast address contains 128 bits, and has the following fields: