Re: Running Alteon back into another switch

Hi Alex,

I think the missing piece is one of the fundamentals of load  
balancing: You need to make sure traffic goes through the Alteon on  
the way out.

Traffic for load balanced servers needs to hit the load balancer on  
the way, and on the way out.  Getting traffic to hit the LB on the way  
in is easy; the VIP address.  Getting traffic through the LB on the  
way out, that's a bit trickier, and you have several options.

By plugging servers directly into the Alteon, you were forcing traffic  
through the Alteon on the way out by it being the server's only  
network connection.  Now that you're plugging the servers into the  
6500, you'll need another method.

If you want to be able to hit the Virtual Service on the Alteon while  
on the same subnet as the servers, you'll have to use proxy IPs  
(warning, this will make it appear to the web servers that all inbound  
web requests come from the Alteon, instead of the true source IP  
address).  By making all requests come from the Proxy IP (PIP) of the  
Alteon, you force traffic through the Alteon on the out.

If you don't have that limitation, i.e. your clients will be on a  
different netblock than the servers, you can use route-path mode by  
setting the default gateway of the servers to the Alteon's floating  
administration IP.  This makes the Alteon the path of traffic on the  
way out, and set the Alteon's default gateway to whatever the server's  
default gateway used to be, so traffic still makes it out to the  
Internet.

So in short, you're options are:  Proxy IP, or route-path (default  
gateway is the Alteon).

Hope that helps, and let me know if you have any questions.

Tony




When you were plugging the servers directly into the Alteon.


On Mar 27, 2009, at 3:23 PM, Alex Thurlow wrote:

> I have an issue which is somewhat of a general networking question,  
> but
> there's a load balancer in the middle of it, so I'm asking here.
>
> Here's my current setup:
>
> A Cisco 6506 has all of my non-load balanced hardware and my uplinks
> plugged into it.  All general ports  are on VLAN 10
>
> 2 bonded Fiber links from the 6506 to an Alteon 184.
>
> 3 load balanced machines plugged directly into the Alteon.  All Alteon
> ports are also VLAN 10
>
> All this works.
>
> What I want to do is, instead of plugging the load balanced machines
> directly into the Alteon, I want to run a link from the Alteon back to
> ports on the 6506 on different VLANs.  Then I can plug as many things
> behind the load balancer as I want as long as I don't go over the
> bandwidth supplied by the links to the alteon and back.
>
> I've been testing this however, and it's not as easy as it seems  
> like it
> should be.
>
> I set 2 ports on the 6506 to:
> switchport
> switchport access vlan 60
> switchport mode access
> no cdp enable
>
> I plugged port 6 (not doing vlan tagging) on the Alteon into one of  
> the
> vlan 60 ports on the 6506 and I plugged a test machine into the other
> vlan 60 port.
>
> I set up a real server on in the Alteon with the IP address of the  
> test
> machine.
>
> After all this, the test machine can access the Alteon and any  
> machines
> connected directly to it, but it can't contact the 6506 or any  
> machines
> hooked to it.
>
> Another note, all machines here are using IP addresses in the same C
> block, if this matters.  Direct Access Mode on the Alteon is on as  
> well,
> so things should be able to access its IP directly.
>
> Anyone know what I'm missing here?
>
> -- 
> Alex Thurlow
> Blastro Networks
>
> http://www.blastro.com
> http://www.roxwel.com
> http://www.yallwire.com
>
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