About IPv6 Address Types and How JUNOS Software for SRX Series Services Gateway and J-series Devices Use Them
This topic explains the types of IP version 6 (IPv6) addresses that JUNOS Software for SRX Series and J-series devices support and how they are used.
IP version 6 (IPv6) includes the following types of addresses:
- Unicast
A unicast address specifies an identifier for a single interface to which packets are delivered. Under IPv6, the vast majority of Internet traffic is foreseen to be unicast, and it is for this reason that the largest assigned block of the IPv6 address space is dedicated to unicast addressing. Unicast addresses include all addresses other than loopback, multicast, link-local-unicast, and unspecified.
For SRX Series and J-series devices, the flow module supports the following kinds of IPv6 unicast packets:
- Pass-through unicast traffic, including traffic from and to virtual routers. The device transmits pass-through traffic according to its routing table.
- Host-inbound traffic from and to devices directly connected
to SRX Series and J Series interfaces. For example, host-inbound traffic
includes logging, routing protocol, and management types of traffic.
The flow module sends these unicast packets to the Routing Engine
and receives them from it. Traffic is processed by the Routing Engine
instead of by the flow module, based on routing protocols defined
for the Routing Engine.
The flow module supports all routing and management protocols that run on the Routing Engine. Some examples are OSPFv3, RIPng, TELNET, and SSH.
- Multicast
A multicast address specifies an identifier for a set of interfaces that typically belong to different nodes. It is identified by a value of 0xFF. IPv6 multicast addresses are distinguished from unicast addresses by the value of the high-order octet of the addresses.
The devices support only host-inbound and host-outbound multicast traffic. Host inbound traffic includes logging, routing protocols, management traffic, and so on.
- Anycast
An anycast address specifies an identifier for a set of interfaces that typically belong to different nodes. A packet with an anycast address is delivered to the nearest node, according to routing protocol rules.
There is no difference between anycast addresses and unicast addresses except for the subnet-router address. For an anycast subnet-router address, the low order bits, typically 64 or more, are zero. Anycast addresses are taken from the unicast address space.
The flow module treats anycast packets in the same way as it handles unicast packets. If an anycast packet is intended for the device, it is treated as host-inbound traffic, and it delivers it to the protocol stack which continues processing it.