User guide

Selecting a Firewall Configuration Mode
User Guide 31
Dynamic IP support on the External interface
If you are supporting dynamic IP addressing, you must choose routed
configuration.
If you choose the Dynamic Host Configuration Protocol (DHCP) option,
the Firebox will request its IP address, gateway, and netmask from a
DHCP server managed by your Internet Service Provider (ISP). This
server can also provide WINS and DNS server information for your
Firebox. If it does not, you must add it manually to your configuration, as
described in “Entering WINS and DNS Server Addresses” on page 58.
You can also change the WINS and DNS values provided by your ISP, if
necessary.
Point-to-Point Protocol over Ethernet (PPPoE) is also supported. As with
DHCP, the Firebox initiates a PPPoE protocol connection to your ISP’s
PPPoE server, which automatically configures your IP address, gateway,
and netmask. However, PPPoE does not propagate DNS and WINS server
information as DHCP does.
If you are using PPPoE on the External interface, you will need the PPP
user name and password when you set up your network. Both username
and password each have a 256-byte capacity.
When the Firebox is configured such that it obtains its IP addresses
dynamically, the following functionality (which requires a static IP
address) is not supported unless you are certain that the dynamic IP
settings sent by your ISP will not change:
• High Availability (not supported on Firebox 500)
•Drop-in mode
•1-to-1 NAT
• Enabling the Firebox as a DVCP server
• BOVPN using Basic DVCP (not supported on factory default Firebox
500)
•MUVPN
• RUVPN with PPTP
Regardless of whether the IP settings are stable, 1-to-1 NAT and external
aliases are not supported when the Firebox is a PPPoE client, and manual
IPSec tunnels are not supported when the Firebox is a DHCP or PPPoE
client.