This is an original planning guide. It is not a vendor manual, an official standard, or legal advice. Example addresses use documentation ranges. Review every command before you paste it.
What this hour is for
Wireshark shows frames. The filter builder drafts a display filter from words you type. A capture is still a copy of traffic. Take it on an interface you administer, for a question in the ticket, and stop when the question is answered.
A SPAN or a mirror is the vendor page, and only for a port you were asked to watch. Do not leave a capture running on a user port. Do not save a file full of credentials. If a password appears, rotate it and delete the file.
Start with a filter you can read, such as a documentation address you have replaced with a lab host you run, and one port. A filter you do not understand is a filter you do not use.
The security desk owns incident response. This page is a beginner capture on your lab, not an investigation of a person.
The change you can finish
Apply nothing during the writing of the note. When the lab window opens, it is one change on the device named in the ticket. Read the draft, then the device, then decide.
Rollback is the file or the revision you saved first. You do not invent a rollback after the only copy is gone.
- Write the question.
- Name the interface you administer.
- Draft a filter and read it.
- Capture only long enough to answer.
- Delete the file if it holds a secret, and rotate that secret.
- Stop the capture.
Mistakes that outlive the command
Wireshark for Beginners goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.
- A standing capture on a user port.
- A filter you cannot explain.
- A file of passwords kept.
- A network you do not administer.
- An investigation of a person from this page.
Decisions to write down
One decision for Wireshark for Beginners: The question is one sentence. The interface is yours. The filter was read. The capture is stopped. And secrets were not kept.
Checks before you call it done
Confirm this before you call the change done: The file location is written or the file was deleted. The filter is in the ticket. The capture duration is short. No foreign network was touched. And a secret, if seen, was rotated. If one of those fails, stop.
One question. Your interface.
Delete a capture that contains a secret.Before you leave the device
Wireshark for Beginners ends when the hostname on the device matches the hostname in the ticket. If it does not, you are on the wrong box. Stop. A command that succeeded on the wrong box is not progress.
The draft stays a draft until a person has read the names in it. A generator does not log into the device and does not know which interface is the uplink. You delete a line that names a device, a zone, or a prefix you did not write down.
0.0.0.0/0 is not kept because a sample included it. A source you can say is the source you keep. 192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24, and 2001:db8::/32 are documentation. They belong in the note. They are not prefixes you type onto a production device because they appeared in a draft.
prompt-for-this is a reminder that a secret is missing. It is not a password, a key, a community string, or a pre-shared key you save in the ticket or in git. The real secret stays in the store.
One change is the window. A VLAN and a routing protocol and a VPN do not share it. If two things move and the result is wrong, you will not know which one did it. The next feature waits for its own page.
If the same step fails twice, stop for the day. The failure is the result. Adding a forum command beside a half-applied config produces a device nobody can rebuild. Restore the copy you took first.
A second person reads the device name and the change aloud. If they cannot find them in the ticket, the note is not done. Silence is not agreement. Then leave the device alone.
This page is a planning guide. It is not a vendor manual, not an official standard, and not a permission to touch a network you do not administer. The pillar guide owns the wider design. This page owns one lab proof.
Tools for this guide
These tools run in the browser on this site. They do not log into your machines.
Related pillar guides
More in this cluster
The pillar for this page, and the next published pages filed with it.
- Pillar: Packet Analysis Guide (Wireshark & tcpdump)
- Cheat Sheet: Wireshark Display Filters Cheat Sheet
- Cheat Sheet: tcpdump Cheat Sheet
- How-To: How to Analyze a PCAP File
Companion: Security: Incident Response Playbook.