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第1章 Introduction
Red Hat OpenStack Platform director creates a cloud environment called the Overcloud. As a default, the Overcloud uses Internet Protocol version 4 (IPv4) to configure the service endpoints. However, the Overcloud also supports Internet Protocol version 6 (IPv6) endpoints, which is useful for organizations that support IPv6 infrastructure. This guide provides information and a configuration example for using IPv6 in your Overcloud.
1.1. Defining IPv6 Networking
IPv6 is the latest version of the Internet Protocol standard. Internet Engineering Task Force (IETF) developed IPv6 as a means to combat the exhaustion of IP address from the current common IPv4 standard. IPv6 has various differences from IPv4 including:
- Large IP Address Range
- The IPv6 range is much larger than the IPv4 range.
- Better End-to-End Connectivity
- The larger IP range provides better end-to-end connectivity due to less reliance on network address translation.
- No Broadcasting
- IPv6 does not support traditional IP broadcasting. Instead, IPv6 uses multicasting to send packets to applicable hosts in a hierarchical manner.
- Stateless Address Autoconfiguration (SLAAC)
- IPv6 provides features for automatically configuring IP addresses and detecting duplicate addresses on a network. This reduces the reliance on a DHCP server to assign addresses.
IPv6 uses 128 bits (represented with 4 hexadecimals using groups of 16 bits) to define addresses while IPv4 only uses only 32 bits (represented with decimal digits using groups of 8 bits). For example, a representation of an IPv4 address (192.168.0.1) looks like this:
| Bits | Representation |
|---|---|
| 11000000 | 192 |
| 10101000 | 168 |
| 00000000 | 0 |
| 00000001 | 1 |
For an IPv6 address (2001:db8:88ec:9fb3::1), the representation looks like this:
| Bits | Representation |
|---|---|
| 0010 0000 0000 0001 | 2001 |
| 0000 1101 1011 1000 | 0db8 |
| 1000 1000 1110 1100 | 88ec |
| 1001 1111 1011 0011 | 9fb3 |
| 0000 0000 0000 0000 | 0000 |
| 0000 0000 0000 0000 | 0000 |
| 0000 0000 0000 0000 | 0000 |
| 0000 0000 0000 0001 | 0001 |
Notice you can also represent IPv6 addresses without leading zeros in each bit group and omit a set of zero bit groups once per IP address. In our example, you can represent the 0db8 bit grouping as just db8 and omit the three sets of 0000 bit groups, which shortens the representation from 2001:0db8:88ec:9fb3:0000:0000:0000:0001 to 2001:db8:88ec:9fb3::1. For more information, see "RFC 5952: A Recommendation for IPv6 Address Text Representation"
Subnetting in IPv6
Similar to IPv4, an IPv6 address uses a bit mask to define the address prefix as its network. For example, if you include a /64 bit mask to our sample IP address (e.g. 2001:db8:88ec:9fb3::1/64) the bit mask acts as a prefix that defines the first 64 bits (2001:db8:88ec:9fb3) as the network. The remaining bits (0000:0000:0000:0001) define the host.
IPv6 also uses some special address types, including:
- Loopback
- The loopback device uses an IPv6 for the internal communication within the host. This device is always ::1/128.
- Link Local
- A link local address is an IP address valid within a particular network segment. IPv6 requires each network device to have a link local address and use the prefix fe80::/10. However, most of the time, these addresses are prefixed with fe80::/64.
- Unique local
- A unique local address is intended for local communication. These addresses use a fc00::/7 prefix.
- Multicast
- Hosts use multicast addresses to join multicast groups. These addresses use a ff00::/8 prefix. For example, FF02::1 is a multicast group for all nodes on the network and FF02::2 is a multicast group for all routers.
- Global Unicast
- These addresses are usually reserved for public IP address. These addresses use a 2000::/3 prefix.
