Frequently Asked Questions

Frequently asked questions about ZLB.

Section 1: Functionality

• How many back-ends can I have in my load-balanced cluster?
• How many distinct ports can I configure to be balanced?
• How can I limit the amount of bandwidth to a certain web site?

Section 2: Installation and Errata

• Problems with FreeBSD 4.6
• Why do I get libdb.so.2 cannot open shared object file messages with Redhat 8.0?
• What is $ZEUSHOME?

Section 3: Fault Diagnosis

• Why does the balancer say a back-end is alive when I think it's dead?
• Why does the balancer say a back-end is dead when I think it's alive?
• I'm getting 'back-end failed' messages in my logs. What's happening and why?
• Why do I get multiple alerts for a single event?
• Why do I get a 'Service unavailable' message from the balancer?
• Why have I received a 'site down' alert when my site appears to be fine?
• My web site isn't working - how can I tell if it is the balancer or the site that is going wrong?

Section 4: Load Balancer Configuration

• How do I replace the license key that Zeus Load Balancer uses?
• What is a tunable?

Section 5: Service Cluster Configuration

• Can I load balance Microsoft FrontPage servers?
• Can I load balance FTP?
• Why do I keep getting 500 Service Unavailable errors?
• How do I get the load balancer to pass through the client IP address to the web server back-ends?
• Why don't my URL mapping rules seem to be working?
• How can I set up a master/slave configuration for my load balanced services?
• Does Zeus Load Balancer support multicast traffic?
• How do I balance multiple SSL sites?
• What protocols can be balanced with the Load Balancer?
• Why do I keep getting Server Misconfigured errors?
• How do I maintain state in my web application?

Section 6: Resilience Configuration

• Can the Load Balancer provide fault tolerance if a back-end server fails whilst delivering a web page?
• I've set up fault tolerance, what's a good way of testing it?
• Does Zeus Load Balancer support Global Load Balancing?
• In a fault-tolerant setup, can I have my traffic IP addresses on multiple network cards?
• Why do I need so many IP addresses to set up fault tolerance?
• Do I need to have two network cards?
• How can I temporarily remove a back-end machine from my load-balanced cluster?
• When I plug a balancer back in, why does it takes so long for the balancer to switch back into use?
• Can I have more than two Zeus Load Balancers configured for fault tolerance?

Section 7: Performance Tuning

• Why does my Zeus Load Balancer not seem to handle more than x connections a second - even though the balancer machines aren't 100% busy?
• Can I run SPECweb or other benchmarks through the balancer?
• My error logs say that I'm running low on file descriptors. How do I make more of them?
• The balancer seems to have lots of connections left open. Why is this?
• How can I use Zeus Load Balancer to speed up slow web servers?

Section 8: Miscellaneous Questions

• Why do SSL connections to IE browsers periodically timeout
• How does the product version numbering scheme used by Zeus work?