F5 how to load balance to servers on an outside/public network

I have an requirement whereby I need to load balance to a server pool which exists outside of the local network where the F5 is present. Basically I require the F5 to direct requests to the servers out of the same interface on which the VIP exists and would like to know if this is possible. Is it a simple matter of creating a VIP, associating the server pool, and ensuring there is a route on the appliance to the server pools? I have attached topology of the scenario.
05/27/09 - Removed Misc Hardware zone; added Servers - Callandor

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giltjrConnect With a Mentor Commented:
I am going to assume that most of the information is dynamic and thus can't be cached.  If this is true, setting up the F5 in London and using the netcache devices in Singapore as the target IP address is going to make users real unhappy with the response time.  Especially if they are accessing this application now.

I personally would push real hard to get the F5 as the first hit and have it do the caching and get the netcache devices out of the picture.  If the netcache devices must stay, I would still put the F5 first with them doing caching, last choice would be to have the F5 first without them doing caching.

Having the netcache devices, then the F5 is not a choice, IMHO.  It adds way to much latency and will impact response time way to much.  

We have applications that with 200ms of latency users are complaining about response time, when we get to 400ms the application is reported as "unusable".

By netcache I am assuming you are talking about the old NetAPP netcache devices.  The stuff that bluecoat purchased awhile back and is planning (or has) killed.
I am fairly sure you can do this, as long as the VIP address and the address on the interface are different.

I have a couple of suggestions (just in case you had not thought about this).

You are going to need to have the F5 to NAT'ing so that the servers see the F5's address IP addresss and not the clients.  If it see's the clients true IP address, the responses will bypass the F5 and attempt go straight back to the client and this will not work.

Can you not use the Cache located in Singapore?  Instead have the F5 do the caching?  This would reduce the amount of traffic that has to flow from the F5 to what ever "Cache" is.

I would also suggest, if you don't have it, to get the compression module and have the F5 do compression.

Any special reason why the F5 can be installed either in NY or Singapore?
sheepsheepAuthor Commented:
The F5 is at a different location and cannot be moved unfortunately :(

We want to test access to the content through the cache so the flow will be something like:
1. Client
2. Cache
3. F5
4. Original Content Servers
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sheepsheepAuthor Commented:
Forgot to add the cache means Netcache.
I have not use netcache, but to men that means that the IP address the user accesses is the netcache devices's, then the netcache device is configured to access the VIP on the F5, which then is configured to access the real servers.

Is the netcache device and the servers in the same data center?  Can it do load balancing?

If the netcache device and the servers are in the same data center, then I personally would do anything and everything NOT to have the setup you have described.  Even if they are not in the same data center.  Not sure, but I beleive that RTT from UK to Singapore is probably about 150 to 200 ms.  That means if the information is not cached you are adding 300-400 ms of overhead, which is a LOT of time.
sheepsheepAuthor Commented:
The cache and the servers are in the same Data room. This setup we have at the moment is out of convenience as we don't have any spare F5's currently. However we are trying to get some into the same room as the cache and servers :)
sheepsheepAuthor Commented:
thanks for all your comments. final solution involved configuring NAT bounceback or snat on the pool and vip.
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