[Netkit.users] problem when simulating link/node down on Netkit

Julien Bisconti julien.bisconti a student.fundp.ac.be
Mer 27 Giu 2007 23:57:17 CEST


Please, see my answer inline,

On 6/27/07, Xu Yao <yaox06 at gmail.com> wrote:
> Hello,
> I am currently using netkit to emulate a lab about MPLS and LDP. I have
> compiled a new kernel, updated the filesystem, installed an
> MPLS-and-LDP-enabled quagga and executed some basic scenarios.

I think you are using mpls-linux and ldp-portable!  I did the same, I will
explain few things that might have impact on your research. By the way, is
the mpls4 module loaded? In other words, is your kernel MPLS enabled? Have
you convert the rpm to deb or have you compiled everything from source code?

Everything worked fine until I tried to simulate a link/node down event. I
> used the command "ifconfig ethx down" and I noticed that the zebra
> process on some of the machines died silently without leaving any log
> files.

I had the similar problem with ldpd (LDP daemon from quagga-mpls), it was
when I configured (by vtysh) the daemon and the interface was connected to
the same collision domain than two others machines. So, for one interface,
ldpd has two next hop. This is explained by the fact that a collision domain
is like a (virtual) hub, every packet sent to this c.d. will be received by
every other machines connected to that c.d.

The thing is sometimes it works, sometimes it doesn't (ldpd crashed) but
when it crashed, I never managed to restart it. In other words, when I
configured all the virtual machines in a specific order, I didn't have the
same "result" (ldpd crashed or it doesn't). I didn't find out what was the
exact cause but I think if the virtual hub were virtual switches, this
problem would be solved. If your problem is coming from the Zebra daemon,
make sure you have uninstalled the old zebra package. Like this you may
avoid conflicts.

I would like to know if anyone has encoutered similar behavior before and
> what can be done to prevent that from happening. Also, is there a better way
> to simulate such an event on Netkit?

FYI, If you want to simulate a node down event, you'd rather use the vcrash
If you want to simulate a link down event, I hope Massimo can help you out
on this because I have no other idea than the "ifconfig ethX down" command.

> Yao

By the way, I think it may be a good idea to post this thread to the
mpls-devel malling list.
I hope it helps,


> Netkit.users mailing list
> Netkit.users at list.dia.uniroma3.it
> http://list.dia.uniroma3.it/mailman/listinfo/netkit.users

Julien BISCONTI <julien.bisconti(at)student.fundp.ac.be>
M.Sc. student in Computer Science, University of Namur
FUNDP, Belgium
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://list.dia.uniroma3.it/mailman/private/netkit.users/attachments/20070627/8e1f8429/attachment.html

Maggiori informazioni sulla lista Netkit.users