IIS and network load balancing

[nitrogen]

This is never how I did it.

I usually use a network load balancing piece of equipment. Currently we use Netscalers. They work like natting firewalls, but this way:

Each web server has a private IP, and the netscaler has a public IP. The netscaler does the load balancing.

Now I'm not a microsoft person, but my bet is this setup works the same way. Let's say you have 5 nodes, 10.0.0.1, 2, 3, 4, and 5, and a public IP of 200.100.90.80. There's only one public IP on one NIC unless youre doing something like NIC teaming.

The packet comes into 200.100.90.80, and that public interface will pick a machine to send teh packet to. Depending on the website's needs, session consistancy is kept or discarded.

[Crossfire]

Russell - I have never tried to implement a Microsoft load balancing solution. Is there a reason you are not using a Cisco solution? Or other routing protocol for whatever switches and routers you have?

[lrb111]

If they use the same ip on the nic, all I can figure is they are being separated out by M.A.C. numbers.

[CodeJockey]

I would definitely use a hardware solution for load balancing. You will find that it works much better than the Microsoft implementation of NLB. Just my $.02.

[pbwalker]

I'll just jump in to say with everyone who has recommended a hardware LB solution. Based on many years of experience, NLB is unstable, cumbersome, and a pain to manage.

I'd recommend a Webmux from RedHill or any of the Cisco CSS line of LB's. Easy VIP maintenance, URI Health Checks, SSL Decryption, and very stable.

It's cool to know there are so many 'geeks' on this board!

[lrb111]

It can. It maybe that there is some sort of port routing, using mac addresses, or hierarchy set in the DNS.

[BigBlueDodge]

Russel NLB is a cooperative system. One incoming request is broadcast to all servers in the cluster. Each server makes a decision on whether to accept the request. The NLB algorithm is written to only allow ONE server in the cluster to accept the request. The algorithm is based on each server knowing information about other servers in the cluster. To find out this other information, each server will periodically send out a heartbeat ping to the other servers. If one server is detected as being offline, NLB will readjust it's algorithms to pull that server out of the cluster.

Many people have asked why are you using NLB. The primary reason is that it is free, and actually works quite well when configured properly. Hardware based load balancers can cost alot of money, and for small farms (2-4 servers) it is hard to justify spending that much money when Windows can do the loadbalancing for free.

[BigBlueDodge]

No worries Russel. Anyone in IT will tell you that in general, a dedicated hardware solution will outperform a software solution and is generally the best choice to go with. If you have the money, then I would always recommend that direction. However, if funds are tight, NLB is 100% able to do what you need. However it is free, and you shouldn't expect it to give you all of the same features as a paid for hardware solution.

[Tahoe132]

To answer your original question, (I am kind of sketchy on this one because I couldn't find it in my text book, I just remember my professor commenting about it) DNS some how points to one of the servers. Some how it can tell the difference and I think there maybe some way to set a priority in them. But I think DNS usually picks the most available one if I remember correctly.

But you should go with Cisco if you are thinking of changing things!! haha.