Tag Archives: network

Did you know that IP addresses (IPv4) can be written in shorter representations?

Did you know that IPv4 addresses can be written in shorter representations, like IPv6 addresses?

Everyone have seen form of IPv6 represented as “shorter form”:
Example from IPv6:

  • 2001::7334
  • ::1
  • ::

You can use our free tool ipv6-literal.com to convert these addresses to long form. The result is:

  • 2001:0000:0000:0000:0000:0000:0000:7334
  • 0000:0000:0000:0000:0000:0000:0000:0001
  • 0000:0000:0000:0000:0000:0000:0000:0000

What admins / programmers usually do not know, is that the same principle applies to IPv4 addresses:

  • 127.1
  • 1
  • 192.168.257
  • 192.168.65535
  • 192.168.65535
  • 192.168
  • 10.1

To test these, use built in ping command. I used ping in Windows 7 and Ubuntu 10, and the result addresses are:

  • 127.1 -> 127.0.0.1
  • 1 -> 0.0.0.1
  • 192.168.257 -> 192.168.1.1
  • 192.168.65535 -> 192.168.255.255
  • 192.168 -> 192.0.0.168
  • 10.1 -> 10.0.0.1

As a bonus, you can try to ping other IP address representations:

  • ping 0x7F000001 – hex
  • ping 010 – octal, does not work in Ubuntu
  • ping 2130706433 – decimal

Why it works this way? Because network funcions built into OS support a such behavior, for example:

Have a fun, and remember, that year of IPv6 is near.

Strange MAC addresses in your network (00:0D:3A:D7:F1:40 – 00:0D:3A:FF:FF:FF)

Today I noticed many strange MAC addresses in our LAN. The addresses looked very similar – only few bits were changing. Sometime this happens, when Ethernet cable is damaged or due to network card malfunction. Here are some sample MAC addresses I observed:

  • 000d3a-fa6109
  • 000d3a-fa6207
  • 000d3a-fa6209
  • 000d3a-fa6107
  • 000d3a-fa6203
  • 000d3a-fa6103
  • 000d3a-fa6212
  • 000d3a-fa6112
  • 000d3a-fa610f
  • 000d3a-fa620f

It turns out, that this time these MAC addresses appeared because someone in our LAN clicked on See full map under Control PanelNetwork and Sharing Center.

Microsoft documentation about Link Layer Topology Discovery (LLTD) Protocol states that:

This protocol defines a range of special MAC addresses that applications can use when they conduct network topology tests. This range is 0x000D3AD7F140 through 0x000D3AFFFFFF. These MAC addresses do not conflict with actual MAC addresses because the range is built from an assigned Organizationally Unique Identifier (OUI)…

Read more here:
http://www.microsoft.com/whdc/connect/rally/lltd-spec.mspx
http://download.microsoft.com/download/a/f/7/af7777e5-7dcd-4800-8a0a-b18336565f5b/LLTD-spec.doc

IPv6, literals and legacy software

IPv4 address exhaustion is slowly going into final phase.

To use IPv6 addresses in legacy software, some mechanism must be in place to not confuse programs with colons (:) in the addresses. For Windows this is IPv6 literals.

We have created IPv6 to literal online converting tool. It is a free tool to convert IPv6 to literal address ending with .ipv6-literal.net

For example, these two lines behave identically:
ping 0--1.ipv6-literal.net
ping ::1

Also, zone ID is supported and shortest / longest IPv6 address form is calculated.

IPv6 literal screenshot

For more information and to test this tool in action, click here!

Use form below, if you have suggestions or comments.

UPDATE Apr 26, 2011. As Takyoji suggested, just added support for Reverse DNS lookup. Now last row is calculated for use with the special domain ip6.arpa.