Permanently set interface in promiscuous mode

The quickest and probably the easiest way to set an interface to promiscuous mode in Linux is to run the following command and add the same to the /etc/rc.local file to survive a reboot.

ifconfig eth0 up promisc

Another option to make it permanent is to edit and update the network configuration file namely /etc/network/interfaces

Remove the lines related to eth0 and update the file to look something like

auto eth0

iface eth0 inet manual

up ifconfig eth0 up promisc

down ifconfig eth0 down -promisc


VLAN Tagging – How to

If you have more than one VLAN on a port (a “trunk port“), you need some way to tell which packet belongs to which VLAN on the other end. To do this you are “tagging” a packet with a VLAN tag (or VLAN header if you like). In reality a VLAN tag is inserted in the Ethernet frame like this:

VLAN Header

The 802.1Q (dot1q, VLAN) tag contains a VLAN-ID and other things explained in the 802.1Q Standard. The first 16 bits contain the “Tag Protocol Identifier” (TPID) which is 8100. This also doubles as the EtherType 0x8100 for devices that don’t understand VLANs.

So a “tagged” packet contains the VLAN information in the Ethernet frame while an “untagged” packet doesn’t. A typical use case would be if you have one port from a router to a switch which multiple customers are attached to:

VLAN Trunking

In this example customer “Green” has VLAN 10 and Customer “Blue” has VLAN 20. The ports between switch and customers are “untagged” meaning for the customer the arriving packet is just a normal Ethernet packet.

The port between router and switch is configured as a trunk port so that both router and switch know which packet belongs to which customer VLAN. On that port the Ethernet frames are tagged with the 802.1Q tag.

How to enable ‘Out of Office’ in a Office 365 Distribution Group

Step-by-step guide

  1. 1. Connect to Exchange Online with Windows PowerShell.
    2. Run the cmdlet:
    Set-DistributionGroup -Identity <DG> -SendOofMessageToOriginatorEnabled $trueNotice
  2. If it is a DDG, please use this command:
    Set-DynamicDistributionGroup -Identity <DDG> -SendOofMessageToOriginatorEnabled $true
  3. Configure a user’s mailbox (which is a member of the DG) in your Outlook and set the OOOM.
  4. Send a test message to the DG to confirm.
  5. In case that Office 365 is syncing with on premises Active Directory then login on clients AD
  6. Locate the Distribution Group -> Properties -> Attribute Editor (Enable Advanced attributes first)
  7. Locate the filed ‘oOFReplyToOriginator‘ and set it to ‘TRUE
  8. Open Powershell and Sync with Office 365 :
  9. Import-Module DirSync
  10. Start-OnlineCoexistenceSync
  11. Configure a user’s mailbox (which is a member of the DG) on your Outlook and set the OOOM.
  12. Send a test message to the DG to confirm