Building Two-Node Directors/Real Servers using LVS and Keepalived

2007-04-27T14:40:08Z

Redgtux: /* Instructions */

== Introduction ==
This guide is a brief explanation on getting a two node director/[[real server]] setup going using [[LVS]] and [[keepalived]].

This is an adaptation of the information at [http://www.ultramonkey.org/2.0.1/topologies/sl-ha-lb-eg.html Ultra Monkey: Streamline High Availablility and Load Balancing] to work with [[keepalived]].

It is primarily targeted at RHEL3/4 (RedHat Enterprise Linux).

== Goals ==
Setup a two node [[LVS]] cluster with Apache as the virtualised services, with both nodes operating as both directors and [[real server]]s. 
Setup healthchecking of services (httpd). 
Setup lvs-syncing of connections (ipvsadm sync daemon). 

== Knowledge Required ==

Understanding of Layer 3 [[load balancing]]. 
Understanding of Linux LVS. 
Understanding of Apache configuration. 

== Components Required ==

Base installation of RHEL3/4. 
RPM Packages for httpd. 
RPM Packages for [[keepalived]]. 
RPM Packages for [[ipvsadm]]. 

== Instructions ==
Install keepalived and IPVSADM on both servers.

On the first server create the file /etc/keepalived/keepalived.conf :

global_defs {
router_id DEV
}
vrrp_instance VI_1 {
state MASTER
interface eth0
virtual_router_id 51
priority 100
advert_int 10
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.6.240
}
}
virtual_server 192.168.6.240 80 {
delay_loop 10
lb_algo rr
lb_kind DR
persistence_timeout 5
protocol TCP
real_server 192.168.6.4 80 {
TCP_CHECK {
}
}
real_server 192.168.6.5 80 {
TCP_CHECK {
}
}
}
}

On the second server create the file /etc/keepalived/keepalived.conf :
global_defs {
router_id DEV
}
vrrp_instance VI_1 {
state BACKUP
interface eth0
virtual_router_id 51
priority 99
advert_int 10
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.6.240
}
}
virtual_server 192.168.6.240 80 {
delay_loop 10
lb_algo rr
lb_kind DR
persistence_timeout 5
protocol TCP
real_server 192.168.6.5 80 {
TCP_CHECK {
}
}
}

On both servers create the file /etc/sysconfig/network-scripts/ifcfg-lo:0
DEVICE=lo:0
IPADDR=192.168.6.240
NETMASK=255.255.255.255
ONBOOT=yes
NAME=loopback

In order to avoid warning messages, we explicitly say that our gateway is on eth0.
Add in /etc/sysconfig/network
GATEWAYDEV=eth0

Add in /etc/sysctl.conf :
net.ipv4.conf.eth0.arp_ignore = 1
net.ipv4.conf.eth0.arp_announce = 2
# Enables packet forwarding
net.ipv4.ip_forward = 1

ifup lo
sysctl -p

== Architecture ==
[[Image:sl-ha-lb-eg.jpg|center]]

{{lvs-example-stub}}

[[Category:LVS Examples|Keepalived]]

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Building Two-Node Directors/Real Servers using LVS and Keepalived