SSCA SIP Troubleshooting & Diagnostic Tools 3

Question 1

A SIP call connects audio flows in one direction only. Which protocol layer should be investigated first?

Accepted Answer

RTP/media path and NAT configuration

Answer

One-way audio is almost always an RTP or NAT problem where media flows correctly in one direction but is blocked or misrouted in the other.

Question 2

What SIP diagnostic tool allows you to send a test OPTIONS message to check if a SIP server is reachable and responsive?

Accepted Answer

sipsak

Answer

sipsak is a command-line SIP Swiss Army knife that can send OPTIONS pings and other SIP requests for testing server reachability.

Question 3

In SIP troubleshooting, what does the Max-Forwards header help diagnose?

Accepted Answer

Routing loops or excessive proxy hops

Answer

Max-Forwards decrements at each hop; if it reaches zero, a 483 Too Many Hops error reveals a routing loop or misconfigured proxy chain.

Question 4

Which response code indicates that a SIP proxy could not find the user in any known location database?

Accepted Answer

404 Not Found

Answer

404 Not Found means the requested user does not exist in the domain or the proxy has no record of them.

Question 5

What is the purpose of the 'sngrep' tool in SIP troubleshooting?

Accepted Answer

It provides a real-time ncurses-based SIP traffic viewer with call flow diagrams

Answer

sngrep is a terminal-based SIP monitor that captures live SIP traffic and displays call flow ladder diagrams in real time.

(SSCA) Sip School Certified Associate Practice Test