indulge me.. DNS/BIND question

[Ares2600]

So I'm trying to get a VERY high throughput benchmark going and we're eating through bandwidth like it's going out of style on our LAN. Trying to figure out a network topology that maximizes the number of Gb links into my cluster so the load drivers have as much room as possible, but I'm limited a bit by the hardware I'm using since it's all extremely low footprint stuff physically. A couple questions:

1) I'm load balancing using my own BIND server and dns round robin. Is there any way to serve up an certain ip address or addresses based on the ip of the requesting host? I.e., look at the originating ip of the query and based on some rule respond with a certain ip address? The trick is that all of the client machines have to hit the same bind server, so I can't solve this by having subsets of the driver machines just point to different dns servers or look up different host names.. they have to use the same dns server and must all look up the same name. I've poked around online but haven't found much on this.. it might be one level higher than my current understanding of zones and BIND configuration.

2) Excuse my ignorance of the nuances of network load balancing as I'm primarily a software guy, but what's the precedent for combining links between two switches to act as a single link? I.e. connect two switches with 4 cables and get a 'simulated' 4Gb link? Ideally just load balancing the packets amongst the links would be fine, but I'm assuming there's some special configurations that would be needed that are likely switch dependent. Are there standards for this sort of thing?

I can't really go into too much detail with respect to the topology as that might give too much away regarding what we're doing, but I'm going to look into it. I really think I have the right building blocks here but need to figure out how to get it all straight and still fulfill the rules of the game.

Thanks in advance for any ideas.

 

[nweaver]

Originally posted by: Ares2600

1) I'm load balancing using my own BIND server and dns round robin. Is there any way to serve up an certain ip address or addresses based on the ip of the requesting host? I.e., look at the originating ip of the query and based on some rule respond with a certain ip address? The trick is that all of the client machines have to hit the same bind server, so I can't solve this by having subsets of the driver machines just point to different dns servers or look up different host names.. they have to use the same dns server and must all look up the same name. I've poked around online but haven't found much on this.. it might be one level higher than my current understanding of zones and BIND configuration.

I'm not understanding you here...

so if Computer A requests name www.myhost.com it should respond with 1.1.1.1, but if host B requests the sam www.myhost.com it should respond with 2.2.2.2?

 

[Ares2600]

Originally posted by: nweaver

I'm not understanding you here...

so if Computer A requests name www.myhost.com it should respond with 1.1.1.1, but if host B requests the sam www.myhost.com it should respond with 2.2.2.2?

Exactly.. good way of putting it.

 

[spidey07]

DNS - not that I know of or have every heard of.

Load Balancing - many different ways to do it. You can create 80-160 Gbs links if need be depending on the gear used.

The thing with load balancing is it depends on what you are trying to load balance and why. Most of the times you load balance on a switch and bond links together. From there it is a question of how you balance the traffic on the link - by source/destination mac address or by source destination IP address. You can see that if most of your traffic is between two IP addresses then you need to look at another means.

And if that's the case then you'll need 10 Gbs network cards and switches.

But if you're problem is interswitch links you would be better off getting a better switch so that all traffic is kept local to a single switch.

 

[Ares2600]

Originally posted by: spidey07
DNS - not that I know of or have every heard of.

Load Balancing - many different ways to do it. You can create 80-160 Gbs links if need be depending on the gear used.

The thing with load balancing is it depends on what you are trying to load balance and why. Most of the times you load balance on a switch and bond links together. From there it is a question of how you balance the traffic on the link - by source/destination mac address or by source destination IP address. You can see that if most of your traffic is between two IP addresses then you need to look at another means.

And if that's the case then you'll need 10 Gbs network cards and switches.

But if you're problem is interswitch links you would be better off getting a better switch so that all traffic is kept local to a single switch.

The source and destination ip's are actually very diverse, so link bonding might be an option for me.. I'll look into that.

There's definitely a much easier way to do this with larger higher quality switches, but my clusters are built of blade hardware, which is limited with respect to the type of switches it can interface with as well as the number of links to the outside world that it has available. I'm going to look further into the network side of things though, especially if the DNS possibilities end up being a bust.

 

[spidey07]

well that is one of the HUGE downsides to blade technology.

but the blades servers that I've seen you can bond multiple gigabit ports to form an etherchannel (cisco only) or Link Aggregation group/802.3ad

 

[randal]

Yes, using bind 9 you can serve up different answers to different hosts based on requesting IP address. This is called `split-horizon` DNS and is very useful for situations where you have a box that does both public DNS resolution and internal (RFC'd/NAT'd) DNS resolution.

It's relatively easy to setup - simply specify the ACLs that you want to match and then point those at the right zone files.

http://www.isc.org/sw/bind/arm93/Bv9ARM.ch04.html#id2549203
http://homepages.tesco.net/J.deBoynePollard/FGA/dns-split-horizon.html

 

[Ares2600]

As usual, you guys rule.. gave me alot to think about thanks.. one or both of those will most likely be useful before I get this stuff humming.

 

[skyking]

Originally posted by: randal
Yes, using bind 9 you can serve up different answers to different hosts based on requesting IP address. This is called `split-horizon` DNS and is very useful for situations where you have a box that does both public DNS resolution and internal (RFC'd/NAT'd) DNS resolution.

It's relatively easy to setup - simply specify the ACLs that you want to match and then point those at the right zone files.

http://www.isc.org/sw/bind/arm93/Bv9ARM.ch04.html#id2549203
http://homepages.tesco.net/J.deBoynePollard/FGA/dns-split-horizon.html

Thanks, Randal. I was going to propose something much more complicated, out in front of a couple of DNS servers.