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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘Ethernet’ Category

`ll header` in `martian source` is the Data Link Layer: 2 MAC addresses

Posted by jpluimers on 2019/06/03

The ll header field in a martian source message on linux is about the [WayBackEthernet frame – Wikipedia: Data Link Layer.

The first 6 hex digits are the source MAC address, the next are the destination MAC address:

May 10 08:59:24 linux kernel: IPv4: martian source 255.255.255.255 from 192.168.17.44, on dev eth1
May 10 08:59:24 linux kernel: ll header: 00000000: ff ff ff ff ff ff 00 0c 29 f7 0f fe 08 00 ........).....

In the above example:

  • Destination = MAC ff ff ff ff ff ff (broadcast, which corresponds with IPv4 target 255.255.255.255)
  • Source = MAC 00 0c 29 f7 0f fe (specific, which I could verify after checking out the machine having IPv4 192.168.17.44)
  • EtherType  08 00 (IPv4)

Some sources indicate it is a martian, as 255.255.255.255 is never a valid IP address, but [WayBack] Martian packet – Wikipedia: IPv4 disagrees.

References:

–jeroen

Posted in Ethernet, Network-and-equipment, Power User | Leave a Comment »

WoL (Wake on LAN) from various routers

Posted by jpluimers on 2019/02/25

Until recently, I hardly used Wake on LAN, so I never noticed that many routers nowadays can send WoL requests themselves.

A few links:

And a few ones from my previous WoL related posts:

–jeroen

Posted in Ethernet, Network-and-equipment, Power User, Wake-on-LAN (WoL) | Leave a Comment »

Windows 7..10: disable shutdown/hibernate/sleep/restart from UI

Posted by jpluimers on 2019/02/18

I needed this for the Windows 10 machine of my mentally retarded brother: WoL (wake-on LAN) for his machine always works when it is in sleep or deep sleep mode, not every now and then fails when fully powered off.

After it is disabled in the UI, you can still perform it with [WayBackshutdown.exe, so I added these shortcuts first:

Disabling the Shutdown related actions in the UI consists of two steps:

  1. Removing it from the logon screen using the registry
  2. Removing it from the user using gpedit.msc (which is wrapped in mmc.exe)

I will try to get the registry changes for the second using [WayBackRegFromApp – Generate RegEdit .reg file from Registry changes made by application (thanks [WayBack] magicandre1981 for suggesting that at [WayBackwindows – How can I use Process Monitor to detect register changes made by GPEdit modifications? – Super User).
The wrapping mmc.exeis easiest to obtain using Process Explorer, and RegFromApp likely needs to run in elevated mode.

If that fails, I can try Process Monitor as suggested by [WayBack] Tom Wijsman in [WayBackcommand line – Change group policy using windows CMD – Super User.

The reason for the above is that I want to avoid UI based modifications that are hard to script.

Remove Shutdown options from the logon screen

This is just the registry setting below.

It also removes the reboot/hibernate/sleep options from the logon screen, so you need shortcuts for that.

Remove Shutdown for the regular users UI

This can be done using either gpedit.msc (Group Policy Editor) drilling down to the local policies or secpol.msc (the Local Policy Editor):

  1. Drill down to
    1. Local Policies
    2. User Rights Management
  2. Double click Shut down the system
  3. Remove the groups you don’t want the system to shutdown
  4. Press OK to confirm

See the video below how.

I’ve removed the group Users and kept the group Administrators to allow ShutDown.

Administrators now do need to execute the above commands (for instance shutdown.exe /h /f) in with an UAC administrative token enabled!

If you do not want that, add the users that can perform Shutdown commands to a new group, then aadd that group to Shutdown the system.

If you want to perform this system wide for all users, then it’s faster to change the [WayBackWindows Explorer NoClose policy (see also [WayBackGroup Policy Registry Reference).

Read the rest of this entry »

Posted in Ethernet, Network-and-equipment, Power User, Wake-on-LAN (WoL), Windows | Leave a Comment »

Raspberry Pi cannot be woken up by WOL, but it can send, and there is Whack-on-LAN

Posted by jpluimers on 2019/01/17

Cool stuff if you want to make your own WOL devices out of spare parts.

From old to new:

They can be woken up by anything sending magic WOL packets, including Raspberry Pi (which cannot be woken up by them, though you could use a Whack-on-LAN for that).

Basically the Raspberry Pi cannot be woken up with WOL because of a few reasons:

  1. The ethernet chip is connected over USB so it cannot pass the WOL result further on.
  2. If it could, there still is no BIOS to process the WOL result.
  3. When it is halted but has power, the CPU isn’t active. The GPU is, but cannot process the WOL.

It can be a WOL server though: [WayBackRaspberry Pi As Wake on LAN Server: 5 Steps (with Pictures)

–jeroen

Posted in Development, Ethernet, Hardware Development, Network-and-equipment, Power User, Raspberry Pi, Wake-on-LAN (WoL) | Leave a Comment »

Strange MAC addresses starting FA:8F:CA without OUI in your network? They are Locally Administered Addresses and likely from Google.

Posted by jpluimers on 2019/01/07

A while ago, I write about Locally Administered Addresses: a few series of MAC addresses you can use on your local network: MAC address ranges safe for testing purposes (Locally Administered Address).

A while ago, I found ones in my network and ones in my WiFi SSID survey starting with FA:8F:CA. They did not show up in the Wireshark · OUI Lookup Tool nor their manufacturer database.

But with bit 7 turned off they start with F8:8F:CA which does show up as “F8:8F:CA Google, Inc.”

They appear to be Google devices, in my case Google ChromeCast ones, though they can also be Google Home ones.

Google does “magic” with networks, just look at a few of the links here:

–jeroen

Posted in Ethernet, Google, Internet, Network-and-equipment, Power User, Ubiquiti, WiFi | Leave a Comment »

 
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