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The meaning of “On-link” in the IPv4 result of the “route print” command (Windows 7, 2008, Vista; via: Super User)

Posted by Jeroen Pluimers on 2012/05/11

The “route print” command in Windows will show you some “On-link” entries in the gateway column. This is from Windows Vista and up. Before that, you would see “127.0.0.1”.

While creating Windows Vista and Windows Server 2008, Microsoft built a “Next Generation TCP/IP Stack” (Wikipedia link) that – apart from adding IPv6 – added many new features and performance improvements.

Since traffic routable through the local machine can have multiple IPv4 and IPv6 addresses, it is not called ” 127.0.0.1″ any more, but “On-link” as the answers to the windows 7 – What does “On-link” mean on the result of “rout print” command? on SuperUser nicely point out:

They are addresses that can be resolved locally. They don’t need a gateway because they dont need to be routed.

and this:

Yep, the other three answers are correct: it’s just a route thats directly reachable the NIC is in direct contact with it; on the same subnet. To explain a little further though: by contrast, the routes that have a gateway IP listed must be contacted through that gateway.

Note that sometimes the new TCP/IP stack needs some arm wrestling in order to have it do what you want (for instance to have it honour TCP metrics).

Note that the “default gateway” line is also missing, as it is in the 0.0.0.0 network destination.

A few examples of what route print shows:

Windows 7 IPv4 route table with some VMware networks:

IPv4 Route Table
===========================================================================
Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0    192.168.171.1  192.168.171.102     20
        127.0.0.0        255.0.0.0         On-link         127.0.0.1    306
        127.0.0.1  255.255.255.255         On-link         127.0.0.1    306
  127.255.255.255  255.255.255.255         On-link         127.0.0.1    306
    192.168.153.0    255.255.255.0         On-link     192.168.153.1    276
    192.168.153.1  255.255.255.255         On-link     192.168.153.1    276
  192.168.153.255  255.255.255.255         On-link     192.168.153.1    276
    192.168.171.0    255.255.255.0         On-link   192.168.171.102    276
  192.168.171.102  255.255.255.255         On-link   192.168.171.102    276
  192.168.171.255  255.255.255.255         On-link   192.168.171.102    276
    192.168.237.0    255.255.255.0         On-link     192.168.237.1    276
    192.168.237.1  255.255.255.255         On-link     192.168.237.1    276
  192.168.237.255  255.255.255.255         On-link     192.168.237.1    276
        224.0.0.0        240.0.0.0         On-link         127.0.0.1    306
        224.0.0.0        240.0.0.0         On-link   192.168.171.102    276
        224.0.0.0        240.0.0.0         On-link     192.168.237.1    276
        224.0.0.0        240.0.0.0         On-link     192.168.153.1    276
  255.255.255.255  255.255.255.255         On-link         127.0.0.1    306
  255.255.255.255  255.255.255.255         On-link   192.168.171.102    276
  255.255.255.255  255.255.255.255         On-link     192.168.237.1    276
  255.255.255.255  255.255.255.255         On-link     192.168.153.1    276
===========================================================================

Windows XP route table with some other VMware networks:

===========================================================================
Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0    192.168.171.1  192.168.171.161      10
        127.0.0.0        255.0.0.0        127.0.0.1       127.0.0.1       1
    192.168.114.0    255.255.255.0    192.168.114.1   192.168.114.1       20
    192.168.114.1  255.255.255.255        127.0.0.1       127.0.0.1       20
  192.168.114.255  255.255.255.255    192.168.114.1   192.168.114.1       20
    192.168.145.0    255.255.255.0    192.168.145.1   192.168.145.1       20
    192.168.145.1  255.255.255.255        127.0.0.1       127.0.0.1       20
  192.168.145.255  255.255.255.255    192.168.145.1   192.168.145.1       20
    192.168.171.0    255.255.255.0  192.168.171.161  192.168.171.161      10
  192.168.171.161  255.255.255.255        127.0.0.1       127.0.0.1       10
  192.168.171.255  255.255.255.255  192.168.171.161  192.168.171.161      10
        224.0.0.0        240.0.0.0    192.168.114.1   192.168.114.1       20
        224.0.0.0        240.0.0.0    192.168.145.1   192.168.145.1       20
        224.0.0.0        240.0.0.0  192.168.171.161  192.168.171.161      10
  255.255.255.255  255.255.255.255    192.168.114.1   192.168.114.1       1
  255.255.255.255  255.255.255.255    192.168.145.1   192.168.145.1       1
  255.255.255.255  255.255.255.255    192.168.145.1               6       1
  255.255.255.255  255.255.255.255  192.168.171.161  192.168.171.161      1
Default Gateway:     192.168.171.1
===========================================================================

and the same XP machine with two NICs to the outside world:

===========================================================================
Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0     192.168.71.1  192.168.71.161       20
          0.0.0.0          0.0.0.0    192.168.171.1  192.168.171.161      10
        127.0.0.0        255.0.0.0        127.0.0.1       127.0.0.1       1
     192.168.71.0    255.255.255.0   192.168.71.161  192.168.71.161       20
   192.168.71.161  255.255.255.255        127.0.0.1       127.0.0.1       20
   192.168.71.255  255.255.255.255   192.168.71.161  192.168.71.161       20
    192.168.114.0    255.255.255.0    192.168.114.1   192.168.114.1       20
    192.168.114.1  255.255.255.255        127.0.0.1       127.0.0.1       20
  192.168.114.255  255.255.255.255    192.168.114.1   192.168.114.1       20
    192.168.145.0    255.255.255.0    192.168.145.1   192.168.145.1       20
    192.168.145.1  255.255.255.255        127.0.0.1       127.0.0.1       20
  192.168.145.255  255.255.255.255    192.168.145.1   192.168.145.1       20
    192.168.171.0    255.255.255.0  192.168.171.161  192.168.171.161      10
  192.168.171.161  255.255.255.255        127.0.0.1       127.0.0.1       10
  192.168.171.255  255.255.255.255  192.168.171.161  192.168.171.161      10
        224.0.0.0        240.0.0.0   192.168.71.161  192.168.71.161       20
        224.0.0.0        240.0.0.0    192.168.114.1   192.168.114.1       20
        224.0.0.0        240.0.0.0    192.168.145.1   192.168.145.1       20
        224.0.0.0        240.0.0.0  192.168.171.161  192.168.171.161      10
  255.255.255.255  255.255.255.255   192.168.71.161  192.168.71.161       1
  255.255.255.255  255.255.255.255   192.168.71.161               6       1
  255.255.255.255  255.255.255.255    192.168.114.1   192.168.114.1       1
  255.255.255.255  255.255.255.255    192.168.145.1   192.168.145.1       1
  255.255.255.255  255.255.255.255  192.168.171.161  192.168.171.161      1
Default Gateway:     192.168.171.1
===========================================================================

–jeroen

via: windows 7 – What does “On-link” mean on the result of “rout print” command? – Super User.

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