Forum Discussion

Bobow's avatar
Icon for Cirrus rankCirrus
Jul 24, 2023

iRule for load balancing to different virtual server depending on the URI path

Hi Guys,

I have three Virtual Server to be configured on our LTM's which are running on the version 15.1.7. One virtual server is facing to client (let say VS-A) and contains two virtual server (let say VS-B and VS-C) that should be load balance.

VS-B and VS-C need to load balance on the VS-A but the incoming traffic should be clasify use the uri /path.

The conditions like this:

if the uri contains /aa, /bb, /cc will be forward and load balance to VS-B and VS-VS-C.

I tried to make irules like this:

if { [HTTP::uri] contains "/aa,/bb,/cc" } {
virtual VS_B
} else {
virtual VS_C

But the results is traffic from the client always going to the VS-B, so the load balancing doesn't have running.

I don't know it can be configured with the iRules or not, since I am not an expert in writing the iRules can anyone suggest me with the iRules that helps working the VIP as mentioned above.

Appreciate any kind your insight.


7 Replies

  • Your description is hard to follow. Can you please provide a flow chart for how you want the different URIs to map to what paths / locations / IPs? Or perhaps a better flow to facilitate understanding of the issue.

      • Bobow This might work but what you are attempting to do seems a whole lot more complicated this way and can most likely be done cleanly by only matching the URI path to a specific destination VS rather than letting load balancing occur and then changing the HOST and URI path after the fact.

        when LB_SELECTED priority 500 {
            set SELECTED_POOL_MEMBER[LB::server addr]
        when HTTP_REQUEST_SEND priority 500 {
            if { ${SELECTED_POOL_MEMBER} == vs_b_ip } {
                HTTP::uri [string map {"/aa" "/"}[HTTP::uri]]
                HTTP::host [string map {"" ""}[HTTP::host]]
            } elseif { ${SELECTED_POOL_MEMBER} == vs_c_ip } {
                HTTP::uri [string map {"/aa" "/"}[HTTP::uri]]
                HTTP::host [string map {"" ""}[HTTP::host]]

        As many have said before "Just because it can be done with an iRule doesn't mean you should." so you might want to look at alternatives that work a bit better. For instance you might consider allowing the servers to listen for the orignal host and uri rather than mapping strings to assist in resolving the issue.

  • wibowo's avatar
    Icon for Nimbostratus rankNimbostratus

    Similler case, need the irules for this one anyone