Posts Tagged ‘ethernet’

XenServer get VM by MAC

Wednesday, December 5th, 2012

Using the GUI, it could be somewhat complex identifying a VM based on its MAC address. There are several solutions on the network using PowerShell, but I will demonstrate it using a simple bash script, below. Save, make executable, and run.



if [ -z "$1" ]
	echo "Requires parameter - MAC address"
	exit 1

# You might want to check MAC correctness here. Enjoy doing it. RegExp, man!

# XenServer is agnostic to case for MAC addresses, so we don't care
VIF_UUID=`xe vif-list MAC=$MAC | grep ^uuid | awk '{print $NF}'`

VM=`xe vif-param-list uuid=$VIF_UUID | grep vm-name-label | awk '{print $NF}'`

echo "MAC $MAC has VM $VM"

x86 Scale Up

Thursday, September 11th, 2008

I have been introduced to a very cool software/hardware combination yesterday. It has been, without exaggerating, one of the coolest things I have seen in a while.

As you may know, x86 has an issue with scaling up. It’s that x86 architectures and price don’t justify scaling up to tenths and hundreds of CPUs. The multi-core technology introduced in the last few years made a four-way server seem trivial today, where in the past it was a high-performance server for large (and expensive) data centers. It is very common today to purchase an eight-way server at a price of a mere commodity server – all thanks to the multi-core technology.

However, when compared to the large Unix data centers, where 64 and 128 cpus are rather common (I will emphasis – the large Unix data centers), although nowadays, per-core, x86 is somewhat more powerful, for a large load set, it could not rival any many-way server. The common solution with x86 was to “scale out” – add more cheap servers and manage the workload in a more distributed way. Yes, you might pay with communication overhead, however, this can be made cheaper still.

With a distributed load sharing came the illnesses of communication latencies. Myrinet, 10Gb/s Ethernet and Infiniband were a common, yet expensive (as it was a niche market) solutions, and still – for distribution of high loads, they were well worth it. Still – a large scaled-up server based on x86 was nowhere to find.

No more. With ScaleMP’s concatenation you can “bundle” a set of servers using Infiniband link into a single huge-multi-way, huge-ram server at a very low cost, relatively.

Think about how you can purchase your current server, for example, your eight-core server (two quad-core cpus), and in time, scale it up into more powerful server (add another two quad-core cpus), or add more RAM, or more network interfaces, or whatever.

This is not as fast as the IBM x3950 board-link (excuse me for not knowing the exact name), so it is not ideal for databases or systems which tend to create a lot of cache-misses, however for large (actually – very large) SMP systems, it could be great. It can allow any company which feels that the current server might not be enough the safety and assurance that they can actually scale up, using the same server, into adding more cpus and more RAM to the server at any time.

I is supported, as far as I know, only for Linux at the time being. It diminishes some of the distance between the large Unix machines and the modern Linux, for a fracture of the price.

I liked it.

Bonding in RedHat RHEL4

Sunday, July 20th, 2008

This is a rather common knowledge now that on RHEL4 you need to state inside /etc/modprobe.conf the following line, when you want more than one bonding interfaces:

options bonding max_bonds=2

Then you attempt to use a trick to address different bonding devices with their name (aka, bond0 and bond1, and maybe bond2, etc), using an option as follows in your /etc/modprobe.conf:

options bond1 -o bond1 miimon=100

It works perfectly fine, until you try to set different parameters for your bonding devices, such as in this example (again, from /etc/modprobe.conf):

options bond0 -o bond0 mode=1 miimon=100
options bond1 -o bond1 mode=1 arp_validate=1 arp_ip_target= arp_interval=1000

These different options will not work. The 2nd (and all next) bonding devices will use bond0’s settings.

A note about this can be found in /usr/share/doc/kernel-doc-2.6.9/Documentation/networking/bonding.txt (requires the package “kernel-doc”):

NOTE: It has been observed that some Red Hat supplied kernels are apparently unable to rename modules at load time (the “-o bond1” part).  Attempts to pass that option to modprobe will produce an “Operation not permitted” error.  This has been reported on some Fedora Core kernels, and has been seen on RHEL 4 as well.  On kernels exhibiting this problem, it will be impossible to configure multiple bonds with differing parameters.

Without the ability to rename modules, we are unable to set, through /etc/modprobe.conf any bond-specific options.

An option which cannot be found in /usr/share/doc/initscripts-7.93.31.EL/sysconfig.txt (part of the “initscripts” package) is to remove any bond-specific parameters from /etc/modprobe.conf and to add to /etc/sysconfig/network-scripts/ifcfg-bondX a line as follows:

BONDING_MODULE_OPTS=’miimon=100 primary=eth0′

Here you can state your bonding options, and when you will restart your networking (provided you actually unload the “bonding” module during that process), your bonds will behave as you expect them to.

A small thing I need to confirm yet is the behavior of the bonding device if settings are changed without unloading the “bonding” module between the ifdown and ifup commands.

Vlan Tagging with bonding network interface on RHEL4

Saturday, May 17th, 2008

This is not a simple task, as there are few things which should actually happen for it to work.

First – the switch port should support vlan tagging (of course, right?)

I have used vlan2 for “external” network, and vlan3 for “internal” network.

My configuration looks like this:











I hope it helps anyone who is into vlan tagging over bonding interfaces.

AP acting as a repeater (WDS protocol) – Apple AirPort as a repeater of Linksys WRT54G

Thursday, September 27th, 2007

In a given place, an AirPort has been connected to the Internet. A Linksys router was added, however, it does not support acting as repeater, however, hidden, there is the ability to act as a WDS master.

The secret is based on the following steps, using the default firmware:

1. Setup Linksys for WEP, setup a key, setup an SSID and a channel.

2. Setup AirPort for WEP, using the same strength, using the same key, same SSID and same channel.

3. Setup AirPort for WDS, acting as “remote base station”. Add the MAC address of the Linksys (I got it using ‘iwlist’ command under Linux, when already connected to it. This is NOT the MAC marked on a sticker at its bottom!)

This should work. Try connecting a client machine to the AirPort Ethernet adapter and renew your DHCP lease to verify it’s working.

Reference taken from this blog. It helped me a lot.