Dual Nic Cards

I have read that many pre-configured machines for Asterisk or FreePBX come with dual nic cards. What is the benifit of dual nics, how would you set them up.



My company’s PBX uses two NICs. One is for connection to the office LAN (obviously). The other NIC gets a static, public IP address. Off-site phones (e.g. home users, retail stores) register to Asterisk via this public IP. Some people advise against putting a PBX on the internet, but if it has a static IP and your remote users do too, you can create rock solid firewall rules.

  • Bobby

On a larger deployment, especially where you have multiple switches, you might want to look a bonding the NICs for redundancy.

Have a look at http://www.cyberciti.biz/tips/linux-bond-or-team-multiple-network-interfaces-nic-into-single-interface.html.

You will want the following in /etc/modprobe.conf:

alias bond0 bonding
options bond0 mode=active-backup miimon=100 primary=eth0

We would like to setup the first NIC as the nic that is connected to the internet (through NAT).

The second NIC I would like to use for a dedicated VOIP netwerk. We would like to use a seperate switch for all VOIP traffic, to make sure that other internet traffic in our office doesn’t disturb the VOIP traffic.

How do we set this up?

For the second NIC, could/should we use DHCP? I think this would be the easiest?

We also need to connect phones (remotely) from out of the office. Would this give routing problems, having Asterisk handle both NIC 1 and 2 for VOIP traffic?


I know this is old, but were you able to proceed with this process? We’ve found our best process is to use bonded nics (for redundancy and performance), which are then assigned a static IP address. We still place the PBX behind a router, but we use Edgewater Networks Edgemarc firewalls, which are excellent at using on premise, or hosted, voip. It includes built-in MOS scoring, survivability, etc. We then use VLANs on the switches to isolate the voice from data.

Do you find that doing things the way you mentioned above (with a public NIC and private NIC) works well?