Difference between revisions of "IPv6 Address"

IPv6 Link-Local Addresses

Link-Local Addresses are used by Nodes to communicate to other Nodes on the same Link. Link-Local addresses are not Routeable.

Windows 7 Link-Local Address Example

Format of Link-Local address

IPv6#<input>sh ipv6 int fa0/0</input>
FastEthernet0/0 is up, line protocol is up
  IPv6 is enabled, <notice>link-local address is FE80::21B:D4FF:FE0F:8CA2</notice>
  No Virtual link-local address(es):
  Description: Outside: Internet connection to ISP
  Global unicast address(es):
    2001:16D8:DD85:146::2, subnet is 2001:16D8:DD85:146::/64
  Joined group address(es):
    FF02::1
    FF02::2
    FF02::D
    FF02::16
    FF02::1:FF00:2
    FF02::1:FF0F:8CA2
  MTU is 1500 bytes
  ICMP error messages limited to one every 100 milliseconds
  ICMP redirects are enabled
  ICMP unreachables are sent
  ND DAD is enabled, number of DAD attempts: 1
  ND reachable time is 30000 milliseconds
  Hosts use stateless autoconfig for addresses.

Example why originating interface is important

Notice in the example below, we telnet to the Heimdal Router - the very same we're on - even I know that the Link-Local address FE80::218:18FF:FE7C:B440 is on a neighboring Router called Campus1.

<notice>Heimdal</notice>#<input>telnet FE80::218:18FF:FE7C:B440</input>
Trying FE80::218:18FF:FE7C:B440 ... Open
 !!!Netadmin Please upgrade the network security!!!
banner motd

User Access Verification

Password:
<notice>Heimdal</notice>><input>exit</input>

[Connection to FE80::218:18FF:FE7C:B440 closed by foreign host]

Link-Local addresses are local on a link. We need to tell on which interface the Link-Address are on. First we need to find the interface on which the address resides.

Heimdal#<input>show ipv6 neighbor | inc B440</input>
FE80::218:18FF:FE7C:B440                    0 0018.187c.b440  STALE <notice>Vl1</notice>

In the output in previous command, it's seen that the Link-Local address lives in Vlan1. Now we telnet from that source-interface - and Voila everything works as expected.

 
<notice>Heimdal</notice>#<input>telnet FE80::218:18FF:FE7C:B440 /source-interface vlan1</input>
Trying FE80::218:18FF:FE7C:B440 ... Open
 !!!Netadmin please upgrade Network Security!!!
banner motd

User Access Verification

Password:
<notice>Campus1</notice>>

Multicast Address Format

The IPv6 Multicast addresses contains two fields describing which kind of Multicast it is. Flag and Scope.

Flag Field

Scope Field

The Scope field is used to limit the Scope of the Multicast Group.

Variable Scope Multicast Addresses

The "meaning" of a Variable Scope or permanently-assigned multicast address is independent of the scope value. For example, if the "NTP servers group" is assigned a permanent multicast address with a group ID of FF0x::101 (hex), then

FF01::101 means all NTP servers on the same interface (i.e., the same node) as the sender.

FF02::101 means all NTP servers on the same link as the sender.

FF05::101 means all NTP servers in the same site as the sender.

FF0E::101 means all NTP servers in the Internet.

• See IANA IPv6 Multicast Address Space Registry

Well Known Multicast examples

Pinging Multicast Addresses

In the first example below By pinging FF02::2 - All Routers on Local-Link - it's seen from the output below that there are two Routers responding

Campus1#<input>ping FF02::2 source vlan 1 repeat 1</input>
Output Interface: <input>vlan 1</input>
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to FF02::2, timeout is 2 seconds:
Packet sent with a source address of FE80::218:18FF:FE7C:B440

Reply to request 0 received from FE80::128C:CFFF:FE96:F76F, 0 ms
Reply to request 0 received from FE80::219:E7FF:FE51:8C0, 0 ms
Success rate is 100 percent (1/1), round-trip min/avg/max = 0/0/0 ms
2 multicast replies and 0 errors.

When pinging FF02::1 - All Nodes on Local-Link - it's seen that there are ten Nodes, including the two Routers from previous example. Using Local-Link address as source.

Campus1#<input>ping FF02::1 source vlan 1 repeat 1</input>
Output Interface: <input>vlan 1</input>
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to FF02::1, timeout is 2 seconds:
Packet sent with a source address of FE80::218:18FF:FE7C:B440

Reply to request 0 received from FE80::22CF:30FF:FEF0:C81A, 0 ms
Reply to request 0 received from FE80::22CF:30FF:FEF0:C880, 0 ms
Reply to request 0 received from FE80::250:56FF:FE8B:C, 0 ms
Reply to request 0 received from FE80::250:56FF:FE8B:3E, 0 ms
Reply to request 0 received from FE80::250:56FF:FE8B:2, 0 ms
Reply to request 0 received from FE80::250:56FF:FE8B:32, 0 ms
Reply to request 0 received from FE80::250:56FF:FE8B:36, 0 ms
Reply to request 0 received from FE80::207:E9FF:FE40:ABF, 0 ms
Reply to request 0 received from FE80::128C:CFFF:FE96:F76F, 0 ms
Reply to request 0 received from FE80::219:E7FF:FE51:8C0, 0 ms
Success rate is 100 percent (1/1), round-trip min/avg/max = 0/0/0 ms
10 multicast replies and 0 errors.

When pinging with Global Unicast as Source Address, some of the nodes respond with their Global Unicast Address. Appently

Campus1#<input>ping FF02::1 source 2001:16D8:DD85:139:218:18FF:FE7C:B441 repeat 1</input>
Output Interface: <input>vlan 139</input>
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to FF02::1, timeout is 2 seconds:
Packet sent with a source address of 2001:16D8:DD85:139:218:18FF:FE7C:B441

Reply to request 0 received from 2001:16D8:DD85:139:250:56FF:FE8B:A, 17 ms
Reply to request 0 received from 2001:16D8:DD85:139:20C:29FF:FE36:45B1, 17 ms
Reply to request 0 received from 2001:16D8:DD85:139:21B:21FF:FE52:917D, 17 ms
Reply to request 0 received from 2001:16D8:DD85:139:216:76FF:FE9F:FEF6, 17 ms
Reply to request 0 received from 2001:16D8:DD85:139:214:5EFF:FE67:614A, 17 ms
Reply to request 0 received from 2001:16D8:DD85:139:20C:29FF:FE4C:C0C, 17 ms
Reply to request 0 received from 2001:16D8:DD85:139:4A5B:39FF:FE5A:A7F7, 17 ms
Reply to request 0 received from 2001:16D8:DD85:139:9221:55FF:FEBC:BD97, 17 ms
Success rate is 100 percent (1/1), round-trip min/avg/max = 17/17/17 ms
8 multicast replies and 0 errors.

RFC's

rfc4291 "IP Version 6 Addressing Architecture" defines new flags in rfc3306 "Unicast-Prefix-based IPv6 Multicast Addresses" and rfc3956 "Embedding the Rendezvous Point (RP) Address in an IPv6 Multicast Address"

IPv4-mapped IPv6 addresses are used in scenarios where IPv6 an IPv6-only application need to communicate with an IPv4 only application using IPv4 packets.

The IPv4-mapped address, 0:0:0:0:0:FFFF:w.x.y.z or ::FFFF:w.x.y.z, is used to represent an IPv4-only node to an IPv6 node. It is used only for internal representation. The IPv4-mapped address is never used as a source or destination address for an IPv6 packet. The IPv6 protocol does not support the use of IPv4-mapped addresses.^[1]

Dual-stack sockets always require IPv6 addresses. The ability to interact with an IPv4 address requires the use of the IPv4-mapped IPv6 address format. Any IPv4 addresses must be represented in the IPv4-mapped IPv6 address format which enables an IPv6 only application to communicate with an IPv4 node. The IPv4-mapped IPv6 address format allows the IPv4 address of an IPv4 node to be represented as an IPv6 address. The IPv4 address is encoded into the low-order 32 bits of the IPv6 address, and the high-order 96 bits hold the fixed prefix 0:0:0:0:0:FFFF. The IPv4-mapped IPv6 address format is specified in RFC 4291. For more information, see www.ietf.org/rfc/rfc4291.txt. The IN6ADDR_SETV4MAPPED macro in Mstcpip.h can be used to convert an IPv4 address to the required IPv4-mapped IPv6 address format.

If the underlying protocol is actually IPv4, then the IPv4 address is mapped into an IPv4-mapped IPv6 address format. That is the, family field in the SOCKADDR structure indicates AF_INET6, but an IPv4-mapped IPv6 address is encoded in the IPv6 address structure. For a dual-stack socket in listening mode, this means that any accepted IPv4 connections will return an IPv4-mapped IPv6 address. For a dual-stack socket that is connecting to an IPv4 destination, the SOCKADDR structure passed to connect must be an IPv4-mapped IPv6 address. Applications must take care to handle these IPv4-mapped IPv6 addresses appropriately and only use them with dual stack sockets. If an IP address is to be passed to a regular IPv4 socket, the address must be a regular IPv4 address not a IPv4-mapped IPv6 address.^[2]

Only seen working application using IPv4-mapped IPv6 addresses is Windows 7 ping!!!

<input>
C:\Users\Henrik thomsen><notice>ping ::ffff:192.168.139.50</notice>

Pinging 192.168.139.50 with 32 bytes of data:
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62

Ping statistics for 192.168.139.50:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 0ms, Maximum = 0ms, Average = 0ms

</input>

or same as

<input>
C:\Users\Henrik thomsen><notice>ping ::ffff:c0a8:8b32</notice>

Pinging 192.168.139.50 with 32 bytes of data:
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62

Ping statistics for 192.168.139.50:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 0ms, Maximum = 0ms, Average = 0ms
</input>