Setup a Secure Resolver using BIND

The purpose of the lab is to setup the resolver on the first server. You should install either BIND or Unbound -- not both.

Change the host name.

sudo hostnamectl set-hostname resolverX.odslab.se

Upgrade base operating system:

sudo apt-get update && sudo apt-get upgrade -y

Uninstall Unbound if previously installed:
```
sudo dpkg --purge unbound
```
Install BIND as the resolver and remove resolve.conf
```
sudo apt-get install -y bind9
```
Configure BIND so that it only listens on localhost only. Note that some of the options below may already be present in the default configuration file.
```
 sudo vim /etc/bind/named.conf.options
```
Add the following configuration options inside the options section:
```
 listen-on-v6 { ::1; };
 listen-on { 127.0.0.1; };
```
Restart BIND9
```
 sudo systemctl restart bind9
```
Verify by using dig. Notice that the AD-flag is set.
```
 dig @127.0.0.1 +dnssec www.opendnssec.org
```
Also try resolving a domain where DNSSEC is broken.
```
dig @127.0.0.1 www.trasigdnssec.se
```
But we can see that in fact the domain does contain the information if we bypass the DNSSEC validation:
```
dig @127.0.0.1 +cd +dnssec www.trasigdnssec.se
```

Provide feedback