Networking, Samba, IoT, and Internal DNS

What is the purpose of connecting a second router to an existing one via Ethernet?

To create a new subnet or isolated network, expanding or segmenting the original LAN.

What is the default private IP range for a home or small network?

192.168.x.x

Why do we use “x” when describing an IP address (e.g., 192.168.x.x)

We use “x” as a wildcard placeholder to represent variable octets in an IP address.
It means that any value in that range (0–255) can go there

What does a "double NAT" problem refer to?

When two routers perform network address translation, isolating devices across subnets.

What command shows your network interfaces and IPs in Ubuntu?

ip a or ip addr show

What is the default gateway typically used for?

It’s the IP address your device uses to send traffic to other networks or the internet.

What command installs Samba on Ubuntu?

sudo apt install samba

What is the Samba configuration file path?

/etc/samba/smb.conf

How do you test Samba configuration for syntax errors?

testparm

What command restarts the Samba service after editing the config?

sudo systemctl restart smbd

How do you add a new Samba user?

sudo smbpasswd -a <username>

What is the purpose of workgroup in Samba?

It identifies the Windows network group the server belongs to (default: WORKGROUP).

What ports does Samba use?

TCP 139, 445 and UDP 137, 138

Where are Samba shared folders typically located?

Commonly under /srv/samba/ or /home/<user>/share

What does “IoT” stand for?

Internet of Things — networked devices that communicate via local or internet connections.

What tool can you use on Android to test connectivity to your network?

The “Ping Tools” or “Network Utilities” app.

What does a successful ping test indicate?

The device and target are connected and reachable on the same network.

Why might a phone fail to connect to a shared folder?

It’s on a different network/subnet or the Samba share permissions are restricted.

What’s the command to see if a device is connected to your LAN?

arp -a or use your router’s device list.

What is DNS used for?

Translating human-readable names (like fileserver.lab.local) into IP addresses.

What command installs the DNS server package?

sudo apt install bind9

What is the configuration file that defines your custom DNS zones?

/etc/bind/named.conf.local

What command checks DNS zone syntax?

sudo named-checkzone <zone_name> <zone_file>

What command restarts the BIND9 DNS service?

sudo systemctl restart bind9

What file holds the forward lookup zone data?

/etc/bind/db.lab.local

What file holds the reverse lookup zone data?

/etc/bind/db.10.168.192

What does a forward lookup zone do?

Maps hostnames → IP addresses (A records)

What does a reverse lookup zone do?

Maps IP addresses → hostnames (PTR records)

What command tests name resolution using your own DNS server?

dig @127.0.0.1 fileserver.lab.local +short

What command tests reverse DNS resolution?

dig -x 192.168.10.100 +short

what does it mean if named-checkzone says “OK”?

Your DNS configuration syntax and zone files are correct.

What’s a common cause of “no current owner name” error in BIND?

Missing $ORIGIN or improper indentation/blank lines in the zone file.

What command reloads BIND9 after editing configs?

sudo systemctl reload bind9

amba share visible but “permission denied”?

Check folder permissions (chmod 777 <folder> for testing) and Samba user access.

DNS doesn’t resolve names?

Check /etc/bind/named.conf.local for correct zone path and syntax.

Reverse lookup fails but forward works?

Verify the PTR record in the reverse zone file and remove typos (like “in-addr-.arpa”).

DNS won’t start after editing zone file?

Run sudo named-checkzone to identify syntax or missing parentheses.

Devices can’t ping each other?

Ensure they are on the same subnet and no firewall is blocking ICMP

How to clear and reload network configurations quickly?

sudo netplan apply