Friday, August 9, 2013

Local link networking on Debian/Linux between server and workstation

My network is based on wireless LAN, which is running at 54MBit/s. Transfering files between two systems therefor is not very fast. I could use wired connections, but cables would need to be pretty long to connect to the router. However the file server and the workstation are located near to each other and both have a free Gigabit LAN link. So why not connect these systems directly?

Both systems run network-manager, whereas the server runs without a graphical/desktop environment. The file /etc/network/interfaces contains this entry related to the LAN devices on both systems:

allow-hotplug eth0
auto eth0

To create the connection it is necessary to have the package avahi-autoipd installed. In a graphical environment is is then as easy as open the network(-manager) preferences dialog, create a new wired connection, change to the IPv4 Settings tab in its Options dialog and choose the Link local only method. Done.

On the server I have no desktop environment. Therefor I wrote the necessary file /etc/NetworkManager/system-connections/LocalLink myself. The UUID value can be obtained via uuid -n 1:

[802-3-ethernet]
duplex=full
mac-address=<MAC-address>

[connection]
id=LocalLink
uuid=<value of: uuid -n 1>
type=802-3-ethernet
timestamp=0
autoconnect=true

[ipv6]
method=auto

[ipv4]
method=link-local

I restarted the manager via service network-manager restart on the server and the link came up too. The direct link was ready.

A note: I was able to create the connection by using a patch cable because my cards are able to handle the situation. On older systems it might be necessary to use a cross-over-cable.

I would really like to use bonding on the wired ethernet and the wireless devices. But the wireless connections are done via router whereas the ethernet connections are created via local link. I think, this is impossible. Any ideas/hints?

2 comments:

  1. Nice overview! Just a note about the note about the "older systems": AFAIK, the standards for gigabit Ethernet make autonegotiation mandatory, so - at least in theory - *every* GigE-capable card should be able to connect to another GigE-capable card without a crossover cable, at least unless the sysadmin has done something weird to explicitly disable autonegotiation :)

    Of course, I do realize - and I also know from experience - that there really are 100Mbit cards still floating around in active use.

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