Difference between revisions of "Link-Local IPv6 Address"

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  |Example        = FE80::21B:D4FF:FE0F:8CA2
 
  |Example        = FE80::21B:D4FF:FE0F:8CA2
 
  |CompareIPv4    = 169.254.0.0/16 Link-Local
 
  |CompareIPv4    = 169.254.0.0/16 Link-Local
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|Desc1          = [http://tools.ietf.org/html/rfc4291 rfc4291]
 
  |Explanation    = These addresses are used on a single link or a non-routed common access network, such as an Ethernet LAN.
 
  |Explanation    = These addresses are used on a single link or a non-routed common access network, such as an Ethernet LAN.
  
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Routers must not forward IPv6 packets if the source or destination contains a link-local address.
 
Routers must not forward IPv6 packets if the source or destination contains a link-local address.
 
}}
 
}}
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=IPv6 Link-Local Addresses=
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==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.
 
Link-Local Addresses are used by Nodes to communicate to other Nodes on the same Link. Link-Local addresses are ''not'' Routeable.
 +
[[Image:Link-Local Address Windows 7.PNG|left|400px|thumb|Windows 7 Link-Local Address Example]]
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{|
 +
|-
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[[Image:Link-Local IPv6 address.png|500px|float|thumb|Format of Link-Local address]]
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|-
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|
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<source lang=cli>
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IPv6#<input>sh ipv6 int fa0/0</input>
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FastEthernet0/0 is up, line protocol is up
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  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
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  Global unicast address(es):
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    2001:16D8:DD85:146::2, subnet is 2001:16D8:DD85:146::/64
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  Joined group address(es):
 +
    FF02::1
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    FF02::2
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    FF02::D
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    FF02::16
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    FF02::1:FF00:2
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    FF02::1:FF0F:8CA2
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  MTU is 1500 bytes
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  ICMP error messages limited to one every 100 milliseconds
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  ICMP redirects are enabled
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  ICMP unreachables are sent
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  ND DAD is enabled, number of DAD attempts: 1
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  ND reachable time is 30000 milliseconds
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  Hosts use stateless autoconfig for addresses.
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</source>
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|-
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|}
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{{Source cli}}
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==Example why originating interface is important==
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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.
 +
<source lang=cli>
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<notice>Heimdal</notice>#<input>telnet FE80::218:18FF:FE7C:B440</input>
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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>
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 +
[Connection to FE80::218:18FF:FE7C:B440 closed by foreign host]
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</source>
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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.
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<source lang=cli>
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Heimdal#<input>show ipv6 neighbor | inc B440</input>
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FE80::218:18FF:FE7C:B440                    0 0018.187c.b440  STALE <notice>Vl1</notice>
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</source>
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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.
 +
<source lang=cli>
 +
<notice>Heimdal</notice>#<input>telnet FE80::218:18FF:FE7C:B440 /source-interface vlan1</input>
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Trying FE80::218:18FF:FE7C:B440 ... Open
 +
!!!Netadmin please upgrade Network Security!!!
 +
banner motd
 +
 +
User Access Verification
 +
 +
Password:
 +
<notice>Campus1</notice>>
 +
</source>
 +
[[Category:CiscoIPv6]]

Latest revision as of 15:28, 15 June 2011

Link-Local
IPv6 Address Type: Link-Local
Prefix: fe80::/10
Local Routeable: No
Global Routeable: No
Global Unique: No
Example: FE80::21B:D4FF:FE0F:8CA2
IPv4 Equivalent: 169.254.0.0/16 Link-Local
Described in: rfc4291
Explanation

These addresses are used on a single link or a non-routed common access network, such as an Ethernet LAN.

They do not need to be unique outside of that link.

Link-local addresses may appear as the source or destination of an IPv6 packet.

Routers must not forward IPv6 packets if the source or destination contains a link-local 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>>
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