# DNS availability by Zabbix agent

## Overview

This template is designed for dns availability monitoring by Zabbix agent via host/posh and doesn't require any external scripts.  

## Requirements

- Zabbix version: 6.0 and higher.
- [`Define user parameters.`](#define-user-parameters)

## Tested versions

This template has been tested on:

- [Debian GNU/Linux 11](http://ftp.debian.org/debian/dists/bullseye/)
- [Windows 11](https://www.microsoft.com/en-us/windows/windows-11)

### Macros used

|Name|Description|Default|
|----|-----------|-------|
|{$REQUEST}|address to check availability|`google.com`|
|{$RESOLVER1}|dns to check availability|`ns3-l2.nic.ru`|
|{$RESOLVER2}|dns to check availability|`ns4-l2.nic.ru`|
|{$RESOLVER3}|dns to check availability|`ns8-l2.nic.ru`|
|{$RESOLVER4}|dns to check availability|`ns4-cloud.nic.ru`|
|{$RESOLVER5}|dns to check availability|`ns8-cloud.nic.ru`|

### Items

|Name|Description|Type|Key and additional info|
|----|-----------|----|-----------------------|
|DNS request|Address for resolve|Calculated|'dns.request'|
|DNS resolver 1 address|Resolver address|Calculated|'dns.resolver1.address'|
|DNS resolver 1 available|Availability of address|Zabbix agent|'dns.resolver1.available[{$REQUEST},{$RESOLVER1}]'|
|DNS resolver 2 address|Resolver address|Calculated|'dns.resolver2.address'|
|DNS resolver 2 available|Availability of address|Zabbix agent|'dns.resolver2.available[{$REQUEST},{$RESOLVER2}]'|
|DNS resolver 3 address|Resolver address|Calculated|'dns.resolver3.address'|
|DNS resolver 3 available|Availability of address|Zabbix agent|'dns.resolver3.available[{$REQUEST},{$RESOLVER3}]'|
|DNS resolver 4 address|Resolver address|Calculated|'dns.resolver4.address'|
|DNS resolver 4 available|Availability of address|Zabbix agent|'dns.resolver4.available[{$REQUEST},{$RESOLVER4}]'|
|DNS resolver 5 address|Resolver address|Calculated|'dns.resolver5.address'|
|DNS resolver 5 available|Availability of address|Zabbix agent|'dns.resolver5.available[{$REQUEST},{$RESOLVER5}]'|

### Triggers

|Name|Description|Expression|Severity|Dependencies and additional info|
|----|-----------|----------|--------|--------------------------------|
|{ITEM.VALUE1} not resolved by any DNS||length(last(/DNS availability by Zabbix agent/dns.request))>0 and last(/DNS availability by Zabbix agent/dns.resolver1.available[{$REQUEST},{$RESOLVER1}],#1)<>1 and last(/DNS availability by Zabbix agent/dns.resolver2.available[{$REQUEST},{$RESOLVER2}],#1)<>1 and last(/DNS availability by Zabbix agent/dns.resolver3.available[{$REQUEST},{$RESOLVER3}],#1)<>1 and last(/DNS availability by Zabbix agent/dns.resolver4.available[{$REQUEST},{$RESOLVER4}],#1)<>1 and last(/DNS availability by Zabbix agent/dns.resolver5.available[{$REQUEST},{$RESOLVER5}],#1)<>1|High|Manual close: No|
|{ITEM.VALUE1} not resolved by {ITEM.VALUE2}||length(last(/DNS availability by Zabbix agent/dns.request))>0 and length(last(/DNS availability by Zabbix agent/dns.resolver1.address))>0 and last(/DNS availability by Zabbix agent/dns.resolver1.available[{$REQUEST},{$RESOLVER1}],#1)<>1|Average|Manual close: No|
|{ITEM.VALUE1} not resolved by {ITEM.VALUE2}||length(last(/DNS availability by Zabbix agent/dns.request))>0 and length(last(/DNS availability by Zabbix agent/dns.resolver2.address))>0 and last(/DNS availability by Zabbix agent/dns.resolver2.available[{$REQUEST},{$RESOLVER2}],#1)<>1|Average|Manual close: No|
|{ITEM.VALUE1} not resolved by {ITEM.VALUE2}||length(last(/DNS availability by Zabbix agent/dns.request))>0 and length(last(/DNS availability by Zabbix agent/dns.resolver3.address))>0 and last(/DNS availability by Zabbix agent/dns.resolver3.available[{$REQUEST},{$RESOLVER3}],#1)<>1|Average|Manual close: No|
|{ITEM.VALUE1} not resolved by {ITEM.VALUE2}||length(last(/DNS availability by Zabbix agent/dns.request))>0 and length(last(/DNS availability by Zabbix agent/dns.resolver4.address))>0 and last(/DNS availability by Zabbix agent/dns.resolver4.available[{$REQUEST},{$RESOLVER4}],#1)<>1|Average|Manual close: No|
|{ITEM.VALUE1} not resolved by {ITEM.VALUE2}||length(last(/DNS availability by Zabbix agent/dns.request))>0 and length(last(/DNS availability by Zabbix agent/dns.resolver5.address))>0 and last(/DNS availability by Zabbix agent/dns.resolver5.available[{$REQUEST},{$RESOLVER5}],#1)<>1|Average|Manual close: No|

### Discovery rules

There are no discovery rules in this template.

### Item prototypes

There are no item prototypes in this template.

### Define user parameters

for Linux:

```bash
tee -a /etc/zabbix/zabbix_agentd.conf > /dev/null <<'EOF'
Timeout=30
UserParameter=dns.resolver1.available[*], host $1 $2 >> /dev/null && echo 1 || echo 0
UserParameter=dns.resolver2.available[*], host $1 $2 >> /dev/null && echo 1 || echo 0
UserParameter=dns.resolver3.available[*], host $1 $2 >> /dev/null && echo 1 || echo 0
UserParameter=dns.resolver4.available[*], host $1 $2 >> /dev/null && echo 1 || echo 0
UserParameter=dns.resolver5.available[*], host $1 $2 >> /dev/null && echo 1 || echo 0
EOF

systemctl restart zabbix-agent
```

for Windows:

```batch
powershell.exe
$text = @"
Timeout=30
UserParameter=dns.resolver1.available[*], powershell.exe -Command "if (Resolve-DnsName -Name $1 -Type A -Server $2 -ErrorAction SilentlyContinue) {return '1'}; return '0'"
UserParameter=dns.resolver2.available[*], powershell.exe -Command "if (Resolve-DnsName -Name $1 -Type A -Server $2 -ErrorAction SilentlyContinue) {return '1'}; return '0'"
UserParameter=dns.resolver3.available[*], powershell.exe -Command "if (Resolve-DnsName -Name $1 -Type A -Server $2 -ErrorAction SilentlyContinue) {return '1'}; return '0'"
UserParameter=dns.resolver4.available[*], powershell.exe -Command "if (Resolve-DnsName -Name $1 -Type A -Server $2 -ErrorAction SilentlyContinue) {return '1'}; return '0'"
UserParameter=dns.resolver5.available[*], powershell.exe -Command "if (Resolve-DnsName -Name $1 -Type A -Server $2 -ErrorAction SilentlyContinue) {return '1'}; return '0'"
"@
$text | Out-File -Append "$env:ProgramFiles\Zabbix Agent\zabbix_agentd.conf" -Encoding "UTF8"
exit

sc stop "Zabbix Agent" && sc start "Zabbix Agent"
```