Addressing Basics
What three settings must every device on an IP network have to communicate correctly?
IP address, subnet mask, default gateway.
What is the purpose of a subnet mask?
To define which part of an IP address is the network versus the host, helping determine if addresses are local.
What is the default gateway used for?
To route packets to destinations outside the local network.
What does the ping tool do?
Sends ICMP echo request messages to check whether a destination responds.
What is the first physical thing to check when diagnosing a connection problem?
— Check cables or wireless connection status / link lights.
Which setting uniquely identifies a device on its local network?
— IP address
For the mask 255.255.255.0, what portion of the IP address indicates the network (for addresses like 192.168.10.x)?
The first three octets (192.168.10) indicate the network
If a device can reach other local devices but cannot reach websites, name two configuration areas that might be the problem.
— Gateway (router) settings and DNS or routing configuration.
Which IP address is the loopback address used to test local TCP/IP software?
127.0.0.1
After confirming the physical connection, what IP-related settings should you confirm next?
IP address, subnet mask, default gateway, and DNS settings.
If a device’s IP address is 192.168.10.25 on a network using mask 255.255.255.0, is the device with address 192.168.10.78 typically on the same local network? Answer yes or no and explain briefly.
Yes. With mask 255.255.255.0, addresses sharing 192.168.10 are on the same subnet.
If a device has IP 10.0.5.12 and mask 255.255.0.0, would 10.0.6.20 be considered local or remote? Explain how you determined this.
Local. With mask 255.255.0.0, the network portion is 10.0, so 10.0.5.12 and 10.0.6.20 share the same network.
What does it usually indicate if traceroute shows failure at the first hop?
A local gateway or local network problem (e.g., gateway unreachable).
Match the ping target to what it tests: (a) 127.0.0.1 (b) your device's IP (c) default gateway — what does each check?
(a) 127.0.0.1 — tests local TCP/IP stack; (b) your device's IP — checks your network configuration; (c) default gateway — tests connection to the router.
List the sequence of tests you would run, in order, to diagnose a device that cannot reach the internet but can reach local devices.
1) Verify physical/wireless link; 2) confirm IP settings; 3) ping default gateway; 4) ping a remote IP (like 8.8.8.8); 5) ping a domain name or test DNS.
Why is it important that no two devices on the same network share the same IP address?
Duplicate IPs cause address conflicts, preventing correct communication for one or both devices.
Convert the mask 255.255.255.0 into CIDR notation (the /n form).
/24
Describe what the default gateway address typically represents on a small home network.
The router's LAN IP that connects the local network to other networks or the internet.
What information does traceroute (tracert) provide that a simple ping does not?
Traceroute shows each hop (router) on the path and where delays or failures occur; ping only tests reachability and latency to a single target.
A user can ping the gateway but traceroute fails after several hops. What does this suggest about the problem's location?
The problem is likely on a remote network, routing beyond the local gateway, or caused by filtering/firewall on an intermediate network.
Give an example of when you would change a device's IP address manually instead of using DHCP.
Examples: assigning a server a fixed IP, port forwarding, or when a device must keep a stable address for remote access.
Explain how a subnet mask helps a device decide whether to send traffic directly or via the default gateway.
The mask shows which bits are network bits; if destination is in same network, device sends directly; otherwise it sends to default gateway.
Explain how routing differs from using a default gateway when a host wants to send packets to a remote network.
The default gateway is the next-hop router for unknown remote destinations; routing involves routers using route tables to forward packets across multiple networks.
If a ping to an IP address succeeds but accessing a domain name fails, which system is most likely at fault and why?
DNS is most likely at fault because name resolution is required to map domain names to IP addresses; successful IP ping shows routing works.
Provide a concise, methodical checklist (5 steps max) for diagnosing network connectivity from local to remote.
Checklist: