Feeds

Getting your virtual hands dirty with virtual networking

You need something to link all those virtual servers

  • alert
  • submit to reddit

Gartner critical capabilities for enterprise endpoint backup

We're all familiar with the concept of a virtual server. However, when planning and implementing a virtualisation project, it's not just the servers that can be and should be virtualised – it's the network too.

Among the first differences that you'll notice when setting up a virtual machine (VM) is the network setup. Naturally, it's not possible physically to plug a VM into the network, but the OS expects to be connected. The answer is a virtual Ethernet adapter which allows an OS inside the VM to operate as if it were physically connected.

Both Microsoft's Hyper-V and VMware's ESX – the virtualisation market leaders – provide virtual networking services in the form not just one or more virtual NICs but virtual switches too. This means that the hypervisor handles all layer 2 accesses to the network, and provides support for standard networking protocols and services such as VLANs. Both hypervisors allow you for example to build virtual networks both inside individual hosts and across hosts, allowing VMs to communicate as if they were physically connected, and to provide a connection internally between the guest machine and its host.

Virtual networking can also help reduce network management overheads

Virtual switches provide the same services as their physical analogues, so you'll find MAC port forwarding tables, the ability to create VLANs, and ESX for example also makes available a SPAN or mirror port to allow network sniffing for diagnostic purposes. The connection is made in the host's RAM so it's virtually instantaneous and free from the kinds of problems that hardware can throw up.

And because you only need one virtual switch per host machine – the host can add as many ports as the network configuration needs – one of the first changes you'll notice once you start consolidating servers is that the number of network ports required drops. If the host supports a large number of VMs and/or they're particularly I/O-intensive, then it may need several physical NICs, but this number should still be smaller than the number of VMs; if not, then one or more of the VMs may benefit from being re-constituted as a physical server. It's always advisable of course to use at least two physical NICs per host anyway, for redundancy and load balancing purposes.

Virtual networking can also help reduce network management overheads, as the virtual switch will incorporate a DHCP server that can deliver IP addresses appropriate to the VM's location and/or subnet, which is a consideration if the implementation of some form of datacentre orchestration is likely.

Ideally too, a virtual switch should be able to apply network policies no matter where in the datacentre the VM resides, such as VLANs and security policies. For example, Cisco's Nexus 1000V virtual switch does this by integrating into VMware's ESX kernel, displacing VMware's virtual switching system to provide services such as security, policy enforcement, automated provisioning and diagnostics. This allows the management of virtual machines as they migrate across physical servers during routine hardware maintenance or while balancing server workloads.

In an ideal world, the datacentre's network hardware infrastructure should be required to change as little as possible on the introduction of virtualisation, apart perhaps from an increased emphasis on the reliability aspects, given the number of servers dependent on each host although clearly some change will be needed. But at the higher layers, the key is to automate as much as possible, aiming for the holy grail of the datacentre as a unified computing fabric. ®

Boost IT visibility and business value

More from The Register

next story
Apple takes blade to 13-inch MacBook Pro with Retina display
Shaves price, not screen on mid-2014 model
iPhone 6 flip tip slips in Aussie's clip: Apple's 'reversible USB' leaks
New plug not compatible with official Type-C, according to fresh rumors
FEAST YOUR EYES: Samsung's Galaxy Alpha has an 'entirely new appearance'
Wow, it looks like nothing else on the market, for sure
YES YES YES! Apple patents mousy, pressure-sensing iVibrator
Fanbois prepare to experience the great Cupertin-O
Steve Jobs had BETTER BALLS than Atari, says Apple mouse designer
Xerox? Pff, not even in the same league as His Jobsiness
TV transport tech, part 1: From server to sofa at the touch of a button
You won't believe how much goes into today's telly tech
Apple analyst: fruity firm set to shift 75 million iPhones
We'll have some of whatever he's having please
Things are looking up in Flappy Bird sequel
'Swing Copters' offers the same gameplay but in a different direction
prev story

Whitepapers

5 things you didn’t know about cloud backup
IT departments are embracing cloud backup, but there’s a lot you need to know before choosing a service provider. Learn all the critical things you need to know.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Build a business case: developing custom apps
Learn how to maximize the value of custom applications by accelerating and simplifying their development.
Rethinking backup and recovery in the modern data center
Combining intelligence, operational analytics, and automation to enable efficient, data-driven IT organizations using the HP ABR approach.
Next gen security for virtualised datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.