Network Connections

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Network Connections

This section describes the process of establishing a basic network connection with the board. Once a network connection is established, the system may be accessed through the servers on the board, including SSH, HTTP, FTP, and Telnet.

Local Area Network

To make a connection to a local area network (LAN), simply connect a standard Ethernet patch cable to the primary Ethernet port on the board. This may be done before or after power has been applied, as the system is set up to allow hot-plugging of the network interface and should automatically re-configure the network settings when a link is detected.

EMAC OE Linux devices are set to attempt a DHCP network configuration by default. If a DHCP server is available on the network that the system is connected to, it will contact the server to secure an IP address lease. If an address has been obtained by DHCP, there are several ways of determining what address has been leased. The easiest way to access this information is to connect to the board through another method (i.e. serial terminal or graphical interface) and run the ifconfig command to determine the address that has been obtained on the eth0 interface. Alternatively, network tools such as packet sniffers can be used to determine what IP address has been leased. The local network administration can determine and provide this information as well by querying the DHCP server tables. The listing below illustrates usage of the ifconfig command to determine the IP address.

root@emac-oe:~# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:50:C2:E6:60:F4
          inet addr:  Bcast:  Mask:
          inet6 addr: fe80::5054:ff:feb1:f83e/64 Scope:Link
          RX packets:1825 errors:0 dropped:0 overruns:0 frame:0
          TX packets:553 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:139124 (135.8 KiB)  TX bytes:50603 (49.4 KiB)
          Interrupt:25 Base address:0xc000

lo        Link encap:Local Loopback
          inet addr:  Mask:
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

If the board fails to obtain a lease from a DHCP server, it will fall back to a static networking configuration. The default settings are detailed in Table 2 below.

Table 2: Default Static IP Settings
IP Address
Subnetwork Mask
Default Gateway
Broadcast Address

Direct Connection

If a LAN connection is not available or desirable, you may make a direct connection to the board. Use an Ethernet crossover cable to connect directly between the workstation and the target board. Apply power to the board once the physical connections have been made.

If a direct connection has been made to the board and a DHCP server is not running on the workstation, DHCP will fail and the system will fall back to the default IP settings in Table 2 above. The network interface on the workstation will then need to be configured to use the same subnetwork mask and broadcast address as the target board with a different IP address that falls in the same subnetwork. See Table 3 below for suggested static network settings if the board is still configured with the default static fall back settings. If the configuration has been changed, adjust these values to match the new settings.

Table 3: Static Network Settings for Direct Connection
IP Address
Subnetwork Mask
Default Gateway Blank or
Broadcast Address

To verify that the connection is working properly, use the ping utility to test that the board responds at the address (assuming default network configuration). The listing below shows an example of a successful ping (Ctrl-c was pressed after five packets).

developer@ldc:~$ ping
PING ( 56(84) bytes of data.
64 bytes from icmp_req=1 ttl=64 time=0.447 ms
64 bytes from icmp_req=2 ttl=64 time=0.213 ms
64 bytes from icmp_req=3 ttl=64 time=0.308 ms
64 bytes from icmp_req=4 ttl=64 time=0.318 ms
64 bytes from icmp_req=5 ttl=64 time=0.251 ms
--- ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 3996ms
rtt min/avg/max/mdev = 0.213/0.307/0.447/0.081 ms

Next Steps

After you have established a connection with your device running EMAC OE Linux, you will need to log into the system.