You receive the notification **Connection failed: Activation of network connection failed**.

Activation of network connection failed

<div class="caution">
<p>Tails cannot hide the information that identifies your phone on the local
network.
If you connect your phone to a:</p>
<ul>
<li><p>A Wi-Fi network, then: the network will knowcan see the MAC
address of your phone. </p>
<p>This has security implications that are discussedwe explain in
our [[documentation on
MAC address anonymization|first_steps/welcome_screen/mac_spoofing]].
Some
phones have a feature to hide the real MAC address of the phone.</p></li>
<li><p>A mMobile data network, then
: the network will beis able to know the identifier of
your SIM card (IMSI)
and also the serial number of your phone (IMEI).</p></li>
</ul>
</div>

<div class="caution">
<p>Tails cannot hide the information that identifies your phone on the local
network. If you connect your phone to a:</p>
<ul>
<li><p>Wi-Fi network: the network can see the MAC
address of your phone.</p>
<p>This has security implications that we explain in our [[documentation on
MAC address anonymization|first_steps/welcome_screen/mac_spoofing]]. Some
phones have a feature to hide the MAC address of the phone.</p></li>
<li><p>Mobile data network: the network is able to know the identifier of
your SIM card (IMSI) and the serial number of your phone (IMEI).</p></li>
</ul>
</div>