Providing Network Professionals The Edge

Cisco IP Phone TFTP File Look Up Order

Once a Cisco IP Phone has received its IP address, VLAN information and TFTP IP address information (see IP Phone Boot Process article) its next … [Read more...]

Original Selsius IP Phone

Selsius Systems was a telecommunications company in Dallas, Texas which developed and marketed some of the first IP telephony products in the … [Read more...]

How to Configure a VWIC2-2MFT-T1/E1 Card on a 2800 Series Router

Enter the following command to determine which WIC slot your VWIC2-2MFT-T1/E1 is installed in: show diag The output of this command will appear … [Read more...]

Cisco 2800 Series ISRs – 2801, 2811, 2821, 2851 Features

The Cisco 2800 series of Integrated Services router platforms are one of my favorites due to their flexibility in accommodating a host of new and … [Read more...]

The Four Enemies of Voice and Video Traffic

It is the never ending battle of real time voice and video traffic against the following evil foursome.  Here is a quick reference of who/what they … [Read more...]

Cisco Gatekeeper Bandwidth Allocation

A Cisco Gatekeeper has a pre-defined bandwidth number which it allocates per call (based on the CODEC being used). These values are not typically … [Read more...]

SIP Response Codes

SIP Response codes are a means of communication for the Session Initiation Protocol.  They are pre-defined responses to SIP Requests which have been … [Read more...]

Cisco IP Phone SCCP (Skinny) Call States

Cisco IP Phone SCCP (Skinny) Call States This is a list of SCCP call states sent by CUCM to SCCP endpoints: 1—Off Hook 2—On Hook 3—Ring … [Read more...]

SRST: Maximum IP Phones and Line DNs Supported Per Platform

SRST (Survivable Remote Site Telephony) provides a mechanism for remote site IP phones to continue to operate in case of WAN failure.  IP phones … [Read more...]

What is GARP (Gratuitous ARP Protection)?

Gratuitous ARP (protection) This is an example of a typical standards based (beneficial) LAN feature which can be used in some cases by the bad … [Read more...]