Tech Tutorial: 364.4 Network High Availability (weight: 5) #
Introduction #
In the world of networking, high availability (HA) is essential to ensure continuous service operation during various failure scenarios. Network High Availability involves the implementation of methodologies and systems that ensure network reliability, uptime, and resilience. This tutorial aims to cover the critical aspects and commands necessary to configure high availability for networks on Linux systems.
Key Knowledge Areas: #
- Redundancy
- Failover
- Load balancing
- High Availability configurations
Utilities: #
- Keepalived
- HAProxy
- Pacemaker
- Corosync
Step-by-Step Guide #
1. Configuring Redundancy with Keepalived #
Keepalived provides simple and robust facilities for load balancing and high availability to Linux systems and Linux-based infrastructures. The configuration of keepalived involves creating a keepalived.conf
file which typically resides in /etc/keepalived/
.
Example: Basic Keepalived Setup #
First, install Keepalived:
sudo apt-get install keepalived
Create or modify the /etc/keepalived/keepalived.conf
:
global_defs {
notification_email {
admin@example.com
}
router_id LVS_DEMO
}
vrrp_instance VI_1 {
state MASTER
interface eth0
virtual_router_id 51
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.1.100
}
}
Explanation:
- global_defs: Global settings for notifications and identification.
- vrrp_instance: Defines a VRRP instance.
- state: Could be MASTER or BACKUP.
- interface: Network interface to listen on.
- virtual_router_id: A unique ID for the VRRP instance.
- priority: Determines the role of MASTER or BACKUP.
- virtual_ipaddress: The IP address shared among the nodes.
Reload the keepalived configuration:
sudo systemctl restart keepalived
Check the status:
systemctl status keepalived
2. Load Balancing with HAProxy #
HAProxy is widely used for providing high availability and load balancing solutions to enhance the reliability of server environments.
Example: Basic HAProxy Configuration #
Install HAProxy:
sudo apt-get install haproxy
Configure HAProxy by editing /etc/haproxy/haproxy.cfg
:
global
log /dev/log local0
maxconn 4000
user haproxy
group haproxy
defaults
mode http
log global
option httplog
timeout connect 5000ms
timeout client 50000ms
timeout server 50000ms
frontend http_front
bind *:80
stats uri /haproxy?stats
default_backend http_back
backend http_back
balance roundrobin
server server1 192.168.1.101:80 check
server server2 192.168.1.102:80 check
Explanation:
- global: Sets global settings.
- defaults: Sets defaults for all proxies.
- frontend: Defines listening ports and other front-end settings.
- backend: Configures backend servers and load balancing method.
Reload HAProxy configuration:
sudo systemctl restart haproxy
3. High Availability with Pacemaker and Corosync #
Pacemaker and Corosync are commonly used together to create a high availability cluster.
Installing and Configuring Corosync #
Install Corosync:
sudo apt-get install corosync
Configure Corosync by editing /etc/corosync/corosync.conf
:
totem {
version: 2
cluster_name: cluster_name
transport: udpu
interface {
ringnumber: 0
bindnetaddr: 192.168.1.0
mcastaddr: 239.255.1.1
mcastport: 5405
}
}
nodelist {
node {
ring0_addr: node1
nodeid: 1
}
node {
ring0_addr: node2
nodeid: 2
}
}
quorum {
provider: corosync_votequorum
}
Start and enable Corosync:
sudo systemctl start corosync
sudo systemctl enable corosync
Installing and Configuring Pacemaker #
Install Pacemaker:
sudo apt-get install pacemaker
Integrate Pacemaker with Corosync:
sudo pcs cluster setup --name cluster_name node1 node2
sudo pcs cluster start --all
Configure a simple resource with Pacemaker:
sudo pcs resource create virtual_ip ocf:heartbeat:IPaddr2 ip=192.168.1.100 cidr_netmask=24 op monitor interval=30s
Check cluster status:
sudo pcs status
Conclusion #
By following the steps outlined in this tutorial, you will be able to configure network high availability using Keepalived, HAProxy, and the combination of Pacemaker and Corosync. These tools are essential for creating resilient networks that can maintain service continuity even during failures. Remember, the key to successful network high availability lies in thorough testing and continuous monitoring of the configured systems.
This tutorial aims to provide a foundational understanding and practical examples to help prepare you for implementing network high availability as covered under exam objective 364.4.