Own DNS server not working (SERVFAIL when trying to find out host's IP)

Question

I've set up a DNS server on VM. When I'm using host with an IP addres, it works well (101.48.168.192.in-addr.arpa domain name pointer s1.home.lan.), but when I try to get domain's IP (eg. host s1.home.lan), I get Host s1.home.lan not found: 2(SERVFAIL) . What has been configured wrong?

Config files:

named.conf.local:

zone "home.lan" {
        type master;
        file "/etc/bind/zones/home.lan.db";
};

zone "48.168.192.in-addr.arpa" {
        type master;
        file "/etc/bind/zones/rev.48.168.192.in-addr.arpa";
};

home.lan.db:

$ORIGIN .
$TTL 3600
home.lan. IN SOA ubuntu.home.lan. hostmaster.home.lan (
        2002010101 ; serial
        8H ; refresh
        4H ; retry
        4W ; expire
        1D ; minimum
)
home.lan. IN NS ubuntu.home.lan.
home.lan. IN MX 10 ubuntu.home.lan.

$ORIGIN home.lan.
localhost       IN      A       127.0.0.1
s1              IN      A       192.168.48.101
s2              IN      A       192.168.48.102
s3              IN      A       192.168.48.103

rev.48.168.192.in-addr.arpa:

@ IN SOA ubuntu.home.lan. hostmaster.home.lan. (
        2002010101 ; serial
        8H ; refresh
        4H ; retry
        4W ; expire
        1D ; minimum
)

        IN      NS      ubuntu.home.lan.
101     IN      PTR     s1.home.lan.
102     IN      PTR     s2.home.lan.
103     IN      PTR     s3.home.lan.

Answer 1

You're defining zone home.lan, specify hosts ubuntu.home.lan as MX and NS, but have no A record for ubuntu.home.lan in your home.lan zone.