Server Network Setup

Network interfaces are assigned to either internal LAN or external WAN gateway roles, and they are configured either by DHCP or through static settings. The AAltsys Server uses either one or two network interfaces, with assigned roles and configuration settings based on interface connections. The first, or primary network interface on a system is assigned to device eth0, and an additional, or secondary interface will be eth1.

Servers with two interfaces may act as gateway computers, routing traffic between an external WAN or the Internet and a local network or LAN. Servers with only one network interface can only act as peers on a LAN. WAN connections are preferrably configured using DHCP, while LAN connections need to be statically set. By convention, gateway connections use the primary interface and local connections use the secondary interface on gateway computers.

This set of conventions allows us to describe how network interfaces should be configured in general, as shown in the following table:

Gateway Server   Local Peer Server
Primary Interface device eth0   Primary Interface device eth0
Connection External WAN   Connection Internal LAN
Configuration set using DHCP   Configuration set using Static
    IP address –> nnn.nnn.nnn.nnn
    Netmask –> 255.nnn.nnn.0
    Gateway –> nnn.nnn.nnn.nnn
    DNS server1 –>
    DNS server2 –>
Secondary Interface device eth1   (Missing or unconfigured)
Connection Internal LAN    
Configuration set Static    
IP address –>    
Netmask –>    
Gateway –> (assigned eth0)    
DNS servers –> (assigned eth0)    

Connecting Interfaces

If two Ethernet adapters are used: connect the primary interface to an Internet gateway such as a cable or DSL modem, and connect the secondary interface to a local area network (LAN) switch which connects workstations and printers.

If one Ethernet adapter is used: connect the primary interface to a local area network (LAN) switch which connects workstations and printers. Connect a router between the LAN switch and an Internet gateway.

The AAltsys Server

The AAltSys Server is configured to operate as an Internet gateway by default, as this allows the server to provide gateway and security functions. Where the server creates a new network behind a cable modem or DSL line which includes a DHCP service, the server can be installed with no configuration changes.

Installing an AAltSys server within an existing network requires changing the configuration of both of the server network interfaces. The primary interface must be changed from External to Internal and from set via DHCP to set Static. The secondary interface must be disabled.


Changes to network configuration in a server should be performed only when no users are active. User network connections will be interrupted when the configuration is saved.

Zentyal Module Configuration

The Zentyal installer asks about network interface configuration in two steps. First check the Configure interface types radio buttons according to your server type, and then click Next:

Configure Interface Types:   Configure Interface types:
eth0 –> External   eth0 –> Internal
eth1 –> Internal    

Next configure the network internal and external interfaces according to the server function. During initial setup, use DHCP to configure network interfaces for a LAN peer server.

Configure network for external...    
eth0 –> DHCP    
Configure network for internal...   Configure network for internal...
eth0 –> Static   eth0 –> DHCP
IP address –> 192.1658.2.241    
Netmask –>    


Existing LANs may use differing internal IP ranges and settings. When integrating a server into an existing LAN, the IP settings for the server must be changed on site. Initial ethernet settings for LAN peer servers, set by DHCP, must be changed to Static during module configuration and then reset to match local LAN requirements.

Static IP

eth0 IP should be static when

  • The WAN gateway does not provide DHCP
  • DHCP results from the WAN gateway do not permit the server to access the Internet
  • The server has a public IP for eth0 assigned by the ISP
  • A local subnet is connected to the server on eth0, and eth1 is not used

Change IP from DHCP to static

  • Connect a network switch to eth1 and plug a workstation into the switch.

  • Set the workstation to obtain its address automatically, i.e., through DHCP.

  • Use commands ipconfig /release and ipconfig /renew, or else reboot the workstation to obtain an address.

  • Open the workstation web browser, and enter one of the following addresses:

  • Login to Zentyal (eBox) using an administrator name and password.

  • Select Core ‣ Network ‣ Interfaces from the left side menu.

    1. On the eth0 tab:
    2. Change Method to Static
    3. Enter your static IP address in IP Address
    4. Select your subnet mask in Netmask ( or similar)
    5. Click Change
  • Navigate to Core ‣ Network ‣ Gateways.

    1. Select (+) Add New
    2. Enter a descriptive name
    3. In IP Address, enter the WAN router gateway address
    4. Select eth0 in Interface
    5. Check the Default box
    6. Click Add
  • Click Save Changes in the Zentyal title bar, and then Save.

Dynamic IP (DHCP)

Change IP from static to DHCP

  • Connect a workstation to the server through a switch on eth1.

  • Obtain an IP address for the workstation using DHCP.

  • Open your web browser, and enter one of the following addresses:

  • Login to Zentyal using an administrator name and password.

  • Navigate to Core ‣ Network ‣ Gateways.

    • Click Delete (Trash Can) next to the gateway entry
  • Navigate to Core ‣ Network ‣ Interfaces ‣ eth0.

    • Change Method to DHCP
    • Click Change
  • Click Save Changes on the Zentyal title bar, and then click Save.

Set Static Gateway with DHCP

  • Login to Zentyal at a workstation or the server.
  • Fix Zentyal 1.5 through 2.0 as per the sidebar.
  • Navigate to Core ‣ Network ‣ Gateways.
  • Click (+) Add next to the gateway entry:
    • Enter the gateway IP address
    • Select Interface eth0
    • Check the box for Default
  • Save Changes in the Zentyal title bar, and click Save.

Console Networking Commands

Use the following commands from a login at the server console or through ssh to check the server’s network configuration.


Use the ifconfig command to display IP settings for the server’s devices:

ifconfig eth0
ifconfig eth1
  • eth0 settings should be either obtained through DHCP or set statically
  • eth1 should be set to


Use this command to test network connectivity:

ping (IP for eth0)
ping (IP for Gateway)
ping (IP for DNS)


Use ip to display network configuration, for instance:

ip route ls table default

(Should return “default via 123.456.789.012 dev eth0,” or other gateway ip)


Use this command to obtain an ip and identify the gateway:

sudo dhclient eth0


Use this command to set a gateway to the Internet:

sudo route add default gw 123.456.789.012


Use dig to find DNS name servers:



Use nslookup to find results returned from DNS servers:

nslookup -query=hinfo


Use this command only when no workstations are logged in:

sudo invoke-rc.d ebox restart