appended url redirect to new pool

you may also have to make sure all embedded object in page is using relative path (not absolute path).

e.g.

 config

root@(B6900-R69-S40)(cfg-sync Standalone)(Active)(/Common)(tmos) list ltm virtual bar
ltm virtual bar {
    destination 100.100.100.41:80
    ip-protocol tcp
    mask 255.255.255.255
    pool foo
    profiles {
        http { }
        tcp { }
    }
    rules {
        qux
    }
    source 0.0.0.0/0
    source-address-translation {
        type automap
    }
    vs-index 3
}
root@(B6900-R69-S40)(cfg-sync Standalone)(Active)(/Common)(tmos) list ltm pool foo
ltm pool foo {
    members {
        200.200.200.101:80 {
            address 200.200.200.101
        }
    }
}
root@(B6900-R69-S40)(cfg-sync Standalone)(Active)(/Common)(tmos) list ltm pool testserver
ltm pool testserver {
    members {
        200.200.200.111:80 {
            address 200.200.200.111
        }
    }
}
root@(B6900-R69-S40)(cfg-sync Standalone)(Active)(/Common)(tmos) list ltm rule qux
ltm rule qux {
    when HTTP_REQUEST {
  if { [string tolower [HTTP::path]] starts_with "/testserver/" } {
    HTTP::uri [string map {/testserver/ /} [HTTP::uri]]
    pool testserver
  }
}
}


 trace

[root@B6900-R69-S40:Active:Standalone] config  ssldump -Aed -nni 0.0 port 80
New TCP connection 1: 100.100.100.3(33050) <-> 100.100.100.41(80)
1407298766.2703 (0.0553)  C>S
---------------------------------------------------------------
HEAD /testserver/something?abc=1234 HTTP/1.1
User-Agent: curl/7.15.5 (i686-redhat-linux-gnu) libcurl/7.15.5 OpenSSL/0.9.8b zlib/1.2.3 libidn/0.6.5
Host: 100.100.100.41
Accept: */*

---------------------------------------------------------------

New TCP connection 2: 200.200.200.40(33050) <-> 200.200.200.111(80)
1407298766.5858 (0.2505)  C>S
---------------------------------------------------------------
HEAD /something?abc=1234 HTTP/1.1
User-Agent: curl/7.15.5 (i686-redhat-linux-gnu) libcurl/7.15.5 OpenSSL/0.9.8b zlib/1.2.3 libidn/0.6.5
Host: 100.100.100.41
Accept: */*

---------------------------------------------------------------