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Monthly Archives: December 2009

On trying to connect to a device that has no DNS or public visibility, connecting via SSH seemed to hang for an almost indefinite period of time.

This can be avoided by stopping the server from performing a reverse DNS lookup against the connecting IP address by adding the following line to the /etc/ssh/sshd_config:

UseDNS    no

The Linksys SRW2024 initially appears to be a little strangled in functionality – the browser based configuration doesn’t work in Linux/Firefox for example, and the command line menu doesn’t allow for extended configuration.  I was actually on the cusp of sending the device back (I don’t really want to have to use a Windows VM to be able to configure a switch), but it turns out there is an option to get into a lightweight IOS style command line interface…

First, connect to the device using the supplied serial cable and Minicom.  The settings for the device need to be 38400 8N1 and flow control needs to Off (contrary to the documentation on the Linksys website!)

When logged in, configure the IP address and turn on SSH management for ease of configuration – change the password from the default (admin/blank).

Next, log in using ssh, and once logged in, hold CTRL+Z, then type lcli.

To create a VLAN:

# configure
(config)# vlan database
(config-vlan)# vlan 993 (enter your VLAN ID of choice here)
(config-vlan)# end

You should now have the VLAN of 993.

This can be verified using the

#show vlan

To assign ports to VLANs:

# configure
(config)# interface range ethernet g21-24
(config-if)# switchport access vlan 993
(config-if)# end

To check,

# show interfaces switchport ethernet g1
# show interfaces switchport ethernet g21

Hope this helps someone….

It is now possible to connect to a Windows machine running Logmein from Linux using a Java browser plugin…..unfortunately if you are using a 64-bit kernel on Ubuntu Karmic, then the java version from the Ubuntu repos is incompatible with the plugin.

To work around this, download https://secure.logmein.com/activex/logmein-client-1.0.387-1.tar.gz, and extract to ~/.mozilla/plugins/ then download and install nspluginwrapper from the repos (sudo apt-get install nspluginwrapper).  Nspluginwrapper is a tool to create a layer of compatibility for non-native browser plugins.

You can then use nspluginwrapper by using:

sudo nspluginwrapper -i ~/.mozilla/plugins/libractrl.so

Restart firefox and navigate to the logmein website again and it should work…

UMA is also known as 3GPP GAN – and is used to provide a an internet based access point for mobile communications over the internet – in for example, areas where signal is weak, but there is a good wireless internet connection, this internet connection can be utilised to provide good quality voice calls over the data network.

Given that there is a distinct lack of documentation on appropriate firewall configuration for UMA on the net, I thought I’d document the ports and protocols required to get this working.

UMA requires:

UDP/500
UDP/4500
IP Protocol 50 (ESP)
IP Protocol 51 (AH)

In the UK this traffic needs to be permitted to the Orange network (no other carriers support this service yet) 193.35.128.0/20 (thanks Andy for this!)