Specifications

B. DHCP - automatic configuration
All the required IP addresses for Internet connection can, alternatively, be automatically retrieved
from an ISP's DHCP server by enabling the DHCP Client option for the interface connected to the
ISP. This option is enabled by first selecting Network > Interfaces and VPN > Ethernet to
display a list of all the interfaces.
Click the G2 interface in the list to display its properties and select the option to enable the
interface as a DHCP client.
Usually, a DHCP Host Name does not need to be specified but can sometimes be used by an ISP
to uniquely identify this Clavister Security Gateway as a particular DHCP client to the ISP's DHCP
server.
On connection to the ISP, all required IP addresses are retrieved automatically from the ISP via
DHCP and cOS Core automatically sets the relevant address objects in the address book with this
information.
For cOS Core to know on which interface to find the public Internet, a route has to be added to
the main cOS Core routing table which specifies that the network all-nets can be found on the
interface connected to the ISP and this route must also have the correct Default Gateway IP
address specified. This all-nets route is added automatically by cOS Core during the DHCP
address retrieval process.
After all IP addresses are set via DHCP and an all-nets route is added, the connection to the
Internet is configured but no traffic can flow to or from the Internet since there is no IP rule
defined that allows it. As was done in the previous option (A) above, we must therefore define an
IP rule that will allow traffic from a designated source interface and source network. (in this
example, the network G3_net and interface G3) to flow to the destination network all-nets and
the destination interface G2.
C. PPPoE setup
Chapter 4: cOS Core Configuration
44