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

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Archive for May 13th, 2016

Buffalo WLAE-AG300N DHCP client is buggy and adds a NULL character to the host name.

Posted by jpluimers on 2016/05/13

Buffalo WLAE-AG300N is one of those buggy DHCP clients… Even running firmware Ver.1.85 (R1.05/B1.00)), it gets the length of the DHCP host name wrong so adds a bogus NULL byte to that name.

@Buffalo: please fix this.

The DHCP client options are of structure Type/Length/Value so a client is supposed to set the length of the hostname to exactly the number of characters.
However there exist buggy clients that either send a length of 1 more and a \00 at the end of the name, or send a fixed length and pad it with \00 as necessary.

Source: DHCP server: Odd active hostname behaviour: some views have null character at the end, some don’t. – MikroTik RouterOS

Fromt a packet capture:

Buffalo WLAE-AG300N gets the length of the DHCP name wrong and inserts an extra NULL character.

Buffalo WLAE-AG300N gets the length of the DHCP name wrong and inserts an extra NULL character.

This besides these devices also not automatically powering up when power goes out and comes back up…

Mikrotik packet capture and viewing it in Wireshark

Anyway: getting and displaying the packet capture was quite easy:

  1. In Winbox (or from the console):
    1. Tools ->
    2. Packet Sniffer ->
    3.  General tab: set filename and file limit, then click Apply
    4. Filter tab: choose the interface, protocol (UDP) and port (67), then click Apply
    5. Click Start
    6. Wait for the DHCP refresh to happen
    7. Click Stop
  2. In Winbox (or from the console):
    1. Files -> Choose the captured file -> Download
  3. In your file manager, ensure the downloaded file gets the .pcap extension
  4. In Wireshark: load the .pcap file and inspect it

 

–jeroen

Posted in Access Points, Buffalo, Internet, MikroTik, Power User, routers | Leave a Comment »

Cool Windows tool of the day: RegJump by SysInternals

Posted by jpluimers on 2016/05/13

RegJump.exe is really cool, and has already there for more than a year (:

This little command-line applet takes a registry path and makes Regedit open to that path. It accepts root keys in standard (e.g. HKEY_LOCAL_MACHINE) and abbreviated form (e.g. HKLM).

usage: regjump <<path>|-c>
-c Copy path from clipboard.
e.g.: regjump HKLM\Software\Microsoft\Windows

–jeroen

via: RegJump.

Posted in Power User, Windows, Windows 7, Windows 8, Windows 8.1, Windows 9, Windows Server 2000, Windows Server 2003, Windows Server 2003 R2, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, Windows Server 2012 R2, Windows Vista, Windows XP | Leave a Comment »

 
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