====== Work within the GRE/PPTP/L2TP/IPIP tunnels ======
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<note important>DPI doesn't parse the tunnels ((tagged VLAN/QINQ and MPLS traffic are not considered as tunnel)) by default, since the traffic of different operators or clients with a conflicting IPs can be transmitted, but for non-standard connection (before BRAS), tunneling parsing is necessary.</note>

In the Lawful Interception prefilter, tunnel parsing is enabled automatically by the presence of the tap_dev parameter. In other cases, you will need to explicitly enable parsing with the configuration parameter in the **/etc/dpi/fastdpi.conf** file

<code>check_tunnels=1</code>

enables parsing PPTP/L2TP/GRE/IPIP tunnels.