====== HA mode using Keepalived ======

High Availability Mode of Trisul ensures that a Trisul cluster always alive in the event of a single node failure. This article describes how it can be configured step by step.


===== Keepalived =====

It is a Linux implementation of the VRRP Protocol which allows for establishing a Virtual IP. We will be using HA based on VRRP protocol in this article.



===== Architecture =====

{{:ha:keepalived-arch.png?400|}}

===== Steps =====



==== 1. Install Trisul Network Analytics on both HA DR nodes. ====
 

<note important>LICENSE: You need the UNLIMITED license to enable redundancy HA and DR features</note>


==== 2. Configure keepalived on both MASTER and SLAVE ====

Follow instructions in [[admin:keepalived|Configure keepalived]]

Ensure the PRIORITY of MASTER is atleast 50 higher than the priority specified in the SLAVE node.


==== 3. Use IPTABLES on MASTER ====


During normal operation both nodes will be in active-active mode. The NETFLOW sent to the MASTER node will be mirrored to the SLAVE node using IPTABLES rule. You can also use the [[https://github.com/trisulnsm/netflow-shim-tunnel|netflow-shim-tunnel]] to accomplish this


iptables DNAT rule



<code>
iptables -t nat -A PREROUTING \
    -p udp -m udp --dport 2055 -j DNAT \
        --to-destination 10.10.100.116

systemctl start iptables

systemctl enable iptables


</code>

Make it persistent using the iptables-services package 


<code>
dnf install iptables iptables-services
</code>

<code>
iptables-save > /etc/sysconfig/iptables
</code>


To list the NAT rule 

<code>
iptables -t nat -v -L -n --line-number 
</code>


To delete (for testing) 

<code>
iptables -t nat -D PREROUTING 1
</code>