Wednesday, April 13, 2011

Part 1: Network Redundancy for Windows Servers: NIC Teaming

To provide network redundancy to a single Windows server, you would first need to have 2 or more NICs. To protect against a single switch failure, you would further need to ensure different NICs are connected to different network switches.

Generally, the most common way is to use hardware vendors' specific NIC teaming solutions, where multiple NICs are grouped and teamed into a single virtual network adapter. And you manage the Virtual Adapter just like how you manage a physical adapter. The most common NIC teaming solutions include:

For each of the vendor solutions, there are various teaming modes. Some protect against single NIC failure, single switch failure or even both (including load-balancing features). For Intel ANS, it supports the following teaming modes:

1) Adapter Fault Tolerance (AFT)
A team of 2 - 8 NICs connect to the same switch. Only 1 NIC is active and others on standby. Use one common IP address and MAC address. A 'failed' active adapter will pass its MAC and IP address to the standby adapter. As the name implied, it only protects against single NIC failure.

2) Switch Fault Tolerance (SFT)
Similar to AFT above, except that NICs are connected to different switches and supports only 2 NICs. In addition to single adapter protection, it protects against single switch failure.

3) Adaptive Load Balancing (ALB)
2 - 8 NICs can be teamed. One NIC receives and all ports transmit using one IP address and multiple MAC addresses. With Receive Load Balancing (RLB) enabled, more than one NIC (of the fastest speed) can receive traffic in load-balancing mode. Work with 1 or more switches.

4) Virtual Machine Load Balancing (VMLB)
Support multiple Hyper-V VMs on a team of 2 - 8 NICs. It provides transmit and receive traffic load balancing across multiple Virtual Machines (VM) bound to the common team interface. In a VMLB team, each VM is associated with one team member for its TX and RX traffic. If only one virtual NIC is bound to the team, or if Hyper-V is removed, then the VMLB team will act like an AFT team.

5) Link Aggregation
In Cisco term, it is known as EtherChannel where 2 - 8 NICs are teamed to the same switch. It uses a common virtual MAC address and IP address. It supports load-balancing across the team members.

NIC Teaming Configuration
Configuring Intel NIC teaming is a pretty straightforward task once you understand the basic network concept. For step-by-step, see this YouTube demo. Nevertheless, it is important to note that Microsoft (see KB254101 and KB968703) does not support vendor specific NIC teaming. If you raise support issues and NIC teaming is in suspect, MS may ask that the NIC teaming be removed.

In my next posting, I would talk about using Microsoft Windows 2008 Routing (RIPv2) for network redundancy as an alternative.


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