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LVS-mini-HOWTO
Joseph Mack
jmack (at) wm7d (dot) net

Copyright ? 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 Joseph Mack

v2008.11 Nov 2008, released under GPL.

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Table of Contents

1. Introduction
1.1. Location of this document
1.2. What an LVS does
2. Minimum Hardware/Network requirements
2.1. Link layer
2.2. Gotchas: you need an outside client (the director and realservers can't access the virtual service)
2.3. Initial service for testing should be telnet (or netcat)
2.4. Test without filter (iptables) rules
2.5. ip aliases
3. Software
3.1. Compiler
3.2. Use the standard kernel
3.3. Use standard utilities (not ifup)
3.4. getting files in packages
3.5. Getting Files: Director
3.6. Realserver OS by forwarding method
3.7. Realservers: Do you need to handle the arp problem?
3.8. Realservers: arp problem by Linux kernel version
3.9. Realservers: Methods of handling the arp problem
3.10. Why netmask=/32 for the VIP in LVS-DR?
3.11. Choose LVS Forwarding Type: LVS-NAT, LVS-DR and LVS-Tun
3.12. multiple forwarding methods
3.13. Configure scripts, tools
3.14. Install - General
3.15. Director kernel - build it yourself
3.16. How do I check to see if my kernel has the ip-vs patch installed?
3.17. Listing symbols in the kernel
3.18. ipvsadm
3.19. Director: check software
3.20. Director kernel: get someone else to do it for you
3.21. Director: compile problems
4. Example 1: LVS using LVS-NAT forwarding
4.1. Setup using the configure script
4.2. Setup by hand
4.3. Test LVS-NAT operation
4.4. Setup LVS-NAT for the service http
5. Example: Setup LVS using LVS-DR forwarding
5.1. VS-DR for the service telnet
5.2. Setup by hand
5.3. Test LVS-DR operation
5.4. Setup LVS-DR for the service http
6. How users have done it
6.1. Dan Browning, LVS-DR on Red Hat 7.2: handling ARP, other misc problems
6.2. Jezz Palmer, setup of LVS squid
6.3. Two Box LVS
7. What if there are problems
7.1. can't patch kernel, can't compile patched kernel
7.2. Can't compile ipvsadm
7.3. ip_tables doesn't work
7.4. ipvsadm gives wierd erroneous output
7.5. Help! My LVS doesn't work
7.6. The client says "connection refused"
7.7. connection times out
7.8. connection hangs; ipvsadm shows entries in InActConn, but none in ActiveConn
7.9. initial connection is delayed, but once connected everything is fine
7.10. rp_filter incorrect
7.11. connection takes several seconds to connect
7.12. Netmask for VIP wrong
7.13. My LVS doesn't loadbalance, the client always goes to the same realserver
7.14. My LVS still doesn't work: what do I do now?
Abstract

Purpose of this document

To show you how to install a Linux Virtual Server (LVS) and to set up a few demonstration virtual servers. No knowlege of the workings of LVS is needed or explained here. You will need to be familiar with configuring Linux. You are expected to use the instructions here to setup your first LVS, if you can't do it any other way.

Once you can get an LVS to work, you should read the docs and the LVS-HOWTO (http://www.austintek.com/LVS/LVS-HOWTO/HOWTO/index.html) to understand how an LVS works and to setup the LVS you want. If you have trouble with your own LVS setup, read the instructions in the LVS-HOWTO introduction (http://www.austintek.com/LVS/LVS-HOWTO/HOWTO/LVS-HOWTO.introduction.html) about getting help, before posting to the mailing list.

1. Introduction
Everything you want to know (code, docs, mailing list, mailing list archives) can be found somewhere on the LVS website

The neccessity of this mini-HOWTO was pointed out by ratz ratz (at) tac (dot) ch who made suggestions for content and who proof-read the text. Other suggestions came from John Cronin jsc3 (at) havoc (dot) gtf (dot) org. This originally was a set of instructions to get an LVS up quickly without having much of an idea of how an LVS worked. However this lead to duplication of instructions in the HOWTO and the mini-HOWTO. Eventually it became easier to move all the instructions to one place. Now the mini-HOWTO contains more than the minimum you need to know to set up a working demonstration LVS.

This document is written in xml.

1.1. Location of this document
On the LVS-HOWTO website and also linked from the LVS documentation page.

1.2. What an LVS does
An LVS is a group of servers with a director that appear to the outside world (a client on the internet) as one server. The LVS can offer more services, or services of higher capacity/throughput, or redundant services (where individual servers can be brought down for maintenance) than is available from a single server. A service is defined here as a connection to a single port, eg telnet, http, https, nntp, ntp, nfs, ntp, ssh, smtp, pop, databases. Multiport services (eg ftp for LVS-NAT) are also handled as a special case. Other multiport protocols (e.g. passive ftp, http/https for e-commerce sites) are handled by LVS persistance or more recently by fwmark in the HOWTO.