IP services
⏱ ~3-min readAceMark Guide
What this topic is really about
SSH uses TCP port 22 to provide an encrypted remote management session. Telnet (the unencrypted predecessor) uses port 23, HTTPS uses 443, and SNMP uses UDP 161. SSH is preferred over Telnet for secure device administration.
PAT (NAT overload) lets many internal hosts share a single public IP by distinguishing sessions with unique source port numbers. Static NAT maps one-to-one; PAT is many-to-one. It does not encrypt or block traffic.
See the mechanism
The DORA exchange is DHCPDISCOVER then OFFER then REQUEST then ACK. A diagram for this topic isn't available yet — the worked example below walks the same reasoning step by step.
An exam-style question, fully explained
Which DHCP message does a client broadcast first when it boots and has no IP?
- Identify what the question tests: Which DHCP message does a client broadcast first when it boots and has no IP.
- The DORA exchange is DHCPDISCOVER then OFFER then REQUEST then ACK.
- The client starts by broadcasting DISCOVER to find any reachable DHCP server.
- OFFER and ACK come from the server; REQUEST is the third message.
Traps the examiner sets
- Read each option carefully — distractors on IP services are designed to look plausible.
- Re-check the exact wording of the question stem before committing to an answer.
- Watch the qualifiers ("always", "only", "except") that flip a correct-looking option.
Test your recall
Answer each from memory — you'll see instantly whether you're right and why.
Run a focused 10-question mini-mock on IP services and see it stick.
Practice more of this topic →