Friday, May 22, 2009

What is a virtual bridge Virbr0 ?

A virtual bridge, can be defined as a device that
bridges virtual interfaces. It provides an easy
means of networking virtual networking devices
such as venet (virtual network) or veth (virtual
ethernet).

Typically, a virtual bridge Virbr0, has point to
point devices such as venet devices. So whenever
traffic is directed from the kernel to one of the
guest VMs / virtual containers, if the vbridge
is configured with the right IP address and subnet
information, it accepts traffic from the kernel.
Internally, the bridge then forwards the packet to
the correct venet interface as it learns their IPs.
So the typical configuration is -

virbr0 ----------> venet0 -----> eth0 192.168.10.2
|
----- > venet 1 -----> eth0 192.168.10.5

In this case virbr0 could have an IP of 192.168.10.7/24.
Hence virbr0 takes all traffic for 192.168.10.0 and
sends it to the venets which are typically point-point
devices.

If you have any questions please post a comment.

Command to ssh tunnel using vncviewer

VNC viewer provides a command line option to
tunnel over ssh, without having to run a separate
ssh session with X window tunneling.
vncviewer -via native@10.49.3.45 vm99:1
The command uses the via switch. In this example,
the vncviewer will reach the display #1 of vm99
by running an ssh session through 10.49.3.45,.
with the user name native. Such a command is
typically useful while accessing virtual machines
(such as KVM guests, OpenVZ containers)
running on other machines.

Thursday, May 21, 2009

Iperf: write2 failed: Operation not permitted

I have seen this error thrown by Iperf over and
over again. Can anyone please post a comment
and let me know why this is happening?

That should be useful. I am guessing this is
because iperf fails to establish an end to end
socket connection between the client and the
sender.

BSE Trading Simulator For Stocks/Shares

For investors who wish to have an experience
trading stocks on the bombay stock exchange,
an excellent facility is provided by the Singapore
Stock exchange. The Singapore stock exchange
provides real time stock quotes, for a real time
trading simulation. This is one among the best
trading simulators available online for free -

http://futuressimulator.sgx.if5.com/Default.aspx

Do give it a shot.

Tuesday, May 19, 2009

What is the Bluetooth sniper riffle

I just learnt today that it is possible to sniff
traffic from bluetooth transmission, such
as from your wireless headset to your cell
phone over almost a mile. The device needed
for doing this is called a bluetooth riffle. More
information on how to build a bluetooth
riffle is available on boing. Considerable
number of news reports are available
on google that discuss how the riffle can
be used to sniff out vulnerabilities.

Sunday, May 17, 2009

3G service in Mumbai, India

Just read an interview from the Mahanagar telecom
Nigam Limited (MTNL) chief about launching a 3G
service in Mumbai and Delhi. Details are not available
as of now. The company is also not discussing possible
avenues for generating revenue for the spectrum
and the towers. Some discussion is bound to issue
with the sharing of cell towers but nothing beyond
that. The chief even fails to quantify a possible time
in the future (1yr+) when they will possibly break
even. This is even when they are hoping to rope
in 1 Lakh subscribers@ Rs1000/mo.

Interesting to know about this development.
It will be nice to see how this affects the share price
in the BSE (bombay stock exchange).