Beware of the details (and VLANs)

A friend today challenged me with this problem on an Ubuntu box:

auto eth2
iface eth2 inet static
    netmask 31

auto eth2.210
iface eth2.210 inet static
    netmask 31

root@box:~# ifup eth2.210
Cannot find device "eth2.210"
Failed to bring up eth2.210.

The first thing coming to mind is “package vlan missing?”, which it was. After installing it, it got more interesting:

root@box:~# ifup eth2.210
Set name-type for VLAN subsystem. Should be visible in /proc/net/vlan/config
ifup: recursion detected for interface eth2 in parent-lock phase
ERROR: trying to add VLAN #210 to IF -:eth2:-  error: File exists
Cannot find device "eth2.210"
Failed to bring up eth2.210

A little poking around showed, that there’s no interface eth2.210 present in the system, but

root@box:~# cat /proc/net/vlan/config 
VLAN Dev name | VLAN ID
rename10       | 210  | eth2

root@box:~# ip l
10: rename10@eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether DE:AD:BE:EF:23:42 brd ff:ff:ff:ff:ff:ff

Deleting the renameNN interface an running ifup again, just created a renameNN+1 interface with kernel log entries like

[7366672.699018] rename14: renamed from eth2.210

I suspected some bugs in /etc/network/if-{,pre-}up.d/ but this even happend, when manually running

ip link add link eth2 name eth2.210 type vlan id 210


ip link add link eth2 name vlan210 type vlan id 210


Continue reading Beware of the details (and VLANs)

Building your own Software Defined Network with Linux and Open Source Tools

Nearly two years ago, I started thinking about a next generation design for the Freifunk Hochstift backbone infrastructure, motivated by the limits and design choices made before (we were young and didn’t know better.. or didn’t listen..).

This post is the starting point of a series of posts about building a software defined wireless ISP network with Linux, a fistful of Open Source tools and low cost hardware.

Continue reading Building your own Software Defined Network with Linux and Open Source Tools

FFRL Routingdays – Learn to build the Internet

Over a year ago we (the Freifunk Rheinland Backbone Operators) organized the FFRL Routindays, a two day event where we gave a hands-on trainig on “How to build the Internet” or any internal network. As of periodic quesions about where to find the slides and videos here’s a summary of all media available of this event.

The event has entirely been in german language, as are all slides and lab guides. This is provided in the hope, that it still might be of some use even for non-german speakers.

The building blocks were

  1. Networking / IP basics
  2. Static routing + bird hands-on Lab
  3. OSPF
  4. eBGP
  5. eBGP -> OSPF redistribution
  6. iBGP
  7. Policy-based Routing

The complete slidedeck is available here. Thanks to the CCC VideoOperation Center, there are recordings of the event avilable on, too.