====== DHCP handling ======
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In order to trace the beginning/end of user session the FastDPI BRAS monitors DHCP requests being received from user equipment.
There are two mutually exclusive monitoring modes which are specified by the '' bras_dhcp_mode '' configuration option in the **fastdpi.conf** file:
  - [[dpi:bras_bng:bras_l2_vlan:bras_l2_vlan_dhcp:bras_l2_vlan_dhcp_relay|DHCP relay agent]] - the fastDPI operates as a DHCP Relay Agent in this mode. \\ DHCP Relay agent mode is intended for networks where DHCP servers are used.\\ The mode is enabled by specifying in fastdpi.conf:<code>bras_dhcp_mode=1</code>
  - [[dpi:bras_bng:bras_l2_vlan:bras_l2_vlan_dhcp:bras_l2_vlan_dhcp_proxy|DHCP Radius proxy]] - the fastDPI  actually operates as a DHCP server by requesting IP address and other parameters from the Radius server indirectly through the fastPCRF. \\ DHCP Radius proxy mode can be used to deploy networks without DHCP servers, i.e. when all the necessary information, the user IP address and other DHCP settings, can be obtained from the Radius server.\\ The mode is enabled by specifying in fastdpi.conf:<code>bras_dhcp_mode=2</code>