During penetration testing  finding the no  of load balancers on the site is always Complicated and clients expects us to determine the same machine with different IP Addresses.below tool works perfect detecting the load balancers.
Load Balancer Detector (LBD), which uses both DNS and HTTP based techniques to detect load balancers. During the tests, we find that the DNS detection works perfectly, however the HTTP based detection techniques, does give false positives at times (which the tool author acknowledges).

code here http://ge.mine.nu/code/lbd

its a script ,save the code in .sh

Usage details

./lbd.sh www.abc.com