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Category: IP Telephony

Tools for a quick SIP diagnostics – ngrep, sipgrep and sngrep

Sometimes there is a need for simple and quick analysis of a SIP server and its call functions. Of course, we should use the well-known tcpdump, mentioned in the article Using tcpdump for SIP diagnostics. However, for some occasional Linux users this may be too difficult and unclear. But actually there exist some simpler utilities, that could work fine, as ngrep, and for me newer, sipgrep and sngrep (love at first sight).

All utils are directly available and can be installed online from Debian repo using apt-get install ngrep sipgrep sngrep.

Set language on Cisco SPA 502G

This post is relevant to all Cicso SPA phones, which have “G” letter in their names. “G” means global (that you can put there languages), not gigabit ethernet (all phones have 100 Mbps interfaces).

First of all, you need to download language files from cisco support page. They are XML files and look like “spa50x_30x_en_v756.xml”. This is for english language. Important is, that you must have two files – for your desired language and for english language. Then set up TFTP server and put there files.

Kamailio Call establishment permission rules


This article talks about deploying permission control mechanism for call establishment in Kamailio SIP Proxy.

In many VoIP solutions, it is crutial to deploy numbering scheme and write down rules where users are/aren't allowed to call.
On top of that, a company can allow the people to call outside, for example to PSTN. The rules can change over time as well as the numbering scheme itself.