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New Member

LocalDirector Server Farm Communication

We are utilizing a Localdirector for load balancing several server farms. Some of which need to communicate amongst themselves using the virtual address. For instance, if real servers A and B have a virtual address AB and real servers C and D have a virtual address CD. We have a need for either real server A or B to talk to the virtual CD. Can the localdirector accomplish this with a single interface, or do we need to segment these servers on a switch and use multiple interfaces on the localdirector?


New Member

Re: LocalDirector Server Farm Communication

I think you’ll have to segment them on different interfaces. Check with Cisco to be sure. Can’t the servers talk to each others real’s?

New Member

Re: LocalDirector Server Farm Communication

OK. Try this approach.

Leave the existing virtual groups as is for mainstream traffic. Create another virtual group for each real server with just that particular real server as a member. For instance, you have vAB which holds rAB. Now create vA which has only A as a member and so on. Then you can configure vA to talk to vCD and so on. You break this down as far as you feel is necessary without over complicating things.

Assign a different IP address to vA and vB and configure them to talk to the IP address at vCD.

Taking things a step further, assuming this is only replication/content traffic, you may want to use a QoS policy to 'control' the traffic flows between servers, so that your site(s) don't suffer....

Hope it helps, or at least starts the thinking process...


New Member

Re: LocalDirector Server Farm Communication

according to cisco LocalDirector must be between the real servers and the Internet cloud that contains the clients. It must see all the packets coming from the clients to the virtual server and all the traffic that comes back in response to the client-to-virtual packets.

In addition, packets from the clients must come in on one interface and go out to the real servers on a different interface. If these rules are not followed, LocalDirector cannot perform load balancing.

so you can't initiate connection from real servers to virtual IP on same local director

anyway you can double confirm this with cisco.


New Member

Re: LocalDirector Server Farm Communication

Local Director info correct,however if you create virtual servers with just a single real server address as a member then you are creating vip-to-vip comms, not real-to-vip or vip-to-real.

It all depends on what type of traffic needs to be passed between vA or vB and CD. If it is only content management traffic then it they should talk. Besides, the question is not about load-balancing traffic in this scenario, it is about direct comms from server to group.....I think!! :)

New Member

Re: LocalDirector Server Farm Communication


I would recommend replacing the LD with the Content Server Switch. The LD is a layer 2 device, so it will only bridge traffic through it. CSS is more intelligent and has switching fabric hardware also.

On the CSS, create 3 VLANS. One for the AB and CD Virtual IPs and thats the CSS-INcoming client traffic side VLAN . VLAN 2 for real servers A, B.

VLAN 3 for real servers C, D. Each VLAN is configured as a circuit on the CSS with its subnet address and Mask. ( Now we're talking IP here and the routing/switching functionality, not the same with LD which has only system IP and a failover IP)

Now if Real A/B need to talk to VIRTUAL CD, CSS automatically does inter-vlan routing to VLAN 1 and its configuration takes it to VLAN 3 =>real C or D.

Cost also is very comparable.

Cisco Employee

Re: LocalDirector Server Farm Communication

Topology is the key here. Depending on who needs to access the virtual is the most important aspect of this type of configuration. If a client from the Internet needs to hit virtual AB, then real server A or B needs to communicate with virtual CD, this can be accomplished by simply placing the real servers C and D on the Internet side of the LD. For instance, client comes through ethernet 0 hits virtual AB and gets load balanced to server B off of ethernet 1. Server B initiates a separate connection to virtual CD and comes through ethernet 1and gets load balanced to server C. Server C responds back through the LD to server B. Server B then responds back to the client.

The above description is typical of web servers being servers A and B and database servers being C and D. If Internet clients need to hit both virtuals AB and CD then this configuration will not work.

If Internet clients need to hit both virtuals AND the each pair of real servers need to hit the other's virtual then you will need to use 3 interfaces of the LD. One for the Internet or client side, one for real servers A and B, and one for real servers C and D.

I hope this helps.

Best regards,

Chip Schneider

Cisco TAC

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