Network

ping <ip_address> -4 -M do -s $((1500-28))
ping <ip_address> -6 -M do -s $((1500-48))

(echo > /dev/tcp/<ip>/<port number>) > /dev/null 2>&1 && echo "success"

echo net.ipv4.ip_forward = 1 >> /etc/sysctl.conf
echo net.ipv6.conf.all.forwarding=1 >> /etc/sysctl.conf

NETWORKING_IPV6=yes

ip link add link ethX name ethX.vlan_id type vlan id vlan_id

ip addr add X.X.X.X/XX dev ethX.vlan_id

ip link set dev ethX.vlan_id up

ip link add link ethX macvlan_name type macvlan mode bridge

ip link add name bridge_name type bridge

ip link set interface_name master bridge_name

ip link set interface_name nomaster

global_defs {
    enable_script_security
    router_id <name>
}

vrrp_script <block name> {
    script "<command>"
    interval <interval in seconds>
    weight <value for priority -253..253>
    user nobody
}

vrrp_track_process <block name> {
    process <name of proccess>
    interval <interval in seconds>
    weight <value for priority -253..253>
    quorum <minimum number of processes for success>
    quorum_max <maximum number of processes for success>
}

vrrp_instance <block name> {
    state <MASTER/BACKUP>
    interface <interface name>
    virtual_router_id <id, must be same>
    priority <0-255>
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass <password>
    }
    unicast_peer {
        <ip other vrrp host>
    }
    virtual_ipaddress {
        <virtual ip>/<mask> dev <interface name> label <interface name>:vip
    }

    track_process {
        <block name>
    }

   track_script {
       <block name>
    }

}

virtual_server <virtual ip> <port> {

    delay_loop <check delay per seconds>
    lvs_sched <rr|wrr|lc|wlc|lblc|sh|mh|dh|fo|ovf|lblcr|sed|nq|twos>
    lvs_method <NAT|DR>
    protocol <TCP|UDP|SCTP>

    real_server <backend ip> <port> {
        weight 1
        HTTP_GET {
            url {
                status_code 200
            }
            connect_timeout <connection timeout>
        }
    }

    real_server <backend ip> <port> {
        weight 1
        HTTP_GET {
            url {
                path /
                status_code 200
            }
            connect_timeout <connection timeout>
        }
    }
}

netstat -at

netstat -p

netstat -ltupn

netstat -lantp | grep ESTABLISHED |awk '{print $5}' | awk -F: '{print $1}' | sort -u