Interface naming across vendors
A small thing that causes real mistakes when you work across platforms.
Writing
Articles
Voice VLANs: why bother separating
Not tidiness. It makes QoS, security and troubleshooting each substantially easier.
Registration failures and NAT
Phones register, then drop off. The binding expired before the phone refreshed it.
Codec choice and bandwidth reality
The codec bit rate understates what a call actually consumes: G.711 needs about a third more, and G.729 nearly four times as much.
Dial plans that do not fight you
Most dial plan trouble is inconsistency about when digits are added or removed.
One-way audio: the usual suspects
Signalling works, one side hears nothing. The cause is almost always in a short list.
SIP call flow for troubleshooting
You do not need to know SIP thoroughly. You need to know where in the exchange it stopped.
Jitter, loss, and what the ear tolerates
Voice quality complaints map to specific measurable conditions. Learn the mapping.
QoS: the parts people skip
Marking traffic achieves nothing on its own. The queue is where the work happens.
When the satellite link is not the problem
The most expensive, least understood component gets blamed for everything. Prove it before escalating.