Questions tagged [voip]

For questions about Voice over Internet Protocol (VoIP) which encompasses various technologies (methods, functions, and encapsulations) for encoding and delivering audio on a network using IP.

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560 views

How do I diagnose a VoIP issue on a Cisco 2811?

Background Our shop consists of approximately 10~12 Cisco IP phones which then connect to their respective workstations. Each phone is connected to the only switch in the shop which is a Cisco 2950 ...
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1answer
53 views

Smart switching calls in a company phone calls

We use VoIP phones in our company. Some people calls and each one connected to first free operator, and each people calls us once a week, we need one more option to make better experience for our ...
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1answer
67 views

VoIP Provider and Phone Number Routing Questions

I am fairly familiar with VoIP and I have my own VoIP PBX, and my provider is Twilio (for Voice) and CallCentric (for Fax). But How do providers like Twilio work exactly? More specifically: How do ...
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1answer
345 views

ESI PBX LAN-only VoIP phone forwarding thru IPSec tunnel - remote router sees packets but not phone, doesn't forward

Okay, so we have an older X-Class ESI PBX system, an ESI IVX 128x FSIII [see below for link]. We have an LNC card installed in it, which allows for the use of up to 12 LAN-only VoIP phones. We have an ...
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1answer
393 views

Is it possible for ISPs to block part of VPN traffic, like UDP traffic only [closed]

My Question isn't about any carrier or ISP, as it might sound. It's about the technical aspect of internet censorship and needs networking experts to help. As you may know, some countries are blocking ...
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2answers
801 views

how to run multiple IP addresses to be allocated off a single Ethernet port. VoIP

Implementing hosted VoIP with connection of desk handset to Apple Macs. Gbit to desktop Cat5, Aruba 2920 PoE J9836 Layer 3 Switch. Line will be separate 10Mb, separate router too. Question: How can ...
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1answer
978 views

Real IP phone in GNS3 Problem

I am trying to link this configuration to a real SPA 303 IP phone but I do not know where to begin with this. I have the physical IP Phone, but I want to run it through the simulated environment that ...
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1answer
1k views

Call incoming from PSTN does not forward to cellphone number

We have a Cisco 2921 connected to an T1 ISDN PRI with Call Manager Express. We are using CP8861 SIP phones. Everything works fine, calling in and out. To better illustrate the problem here's an ...
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1answer
1k views

How to use a layer 3 switch for QOS between gateway and hosts?

In the following scenario, is it possible to prioritize VOIP/RTP from x.x.x.51 through the gateway with a Cisco switch, and how? I need to prevent x.x.x.50 from saturating the WAN connection. ...
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1answer
684 views

How does “dual-line” feature work on Cisco/Avaya IP phones for VOIP?

For below CME configuration which I configured on UC500 where ephones are not configured with dual-line feature and in button command separator 'c'(call waiting) is used. CME_VOICE(config)#ephone-dn ...
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2answers
783 views

Convert encrypted SRTP to RTP for private network [closed]

Let's say that Alice would like to make SIP call to Bob. Alice initiates the call using her mobile device over a cellular network. On the other hand, Bob sits in a local network of an organisation. ...
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0answers
5k views

RTP Port Number

Hi, In the screenshot UDP Source Port for RTP is 8000 and Destination Port is 40376. Standard port Numbers for RTP are 16384-32767. Even if we change the standard port range, should it not be min. ...
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1answer
4k views

Why and when do we use digit '9' before making an outbound call?

Also explain when do we use this feature (Please explain for both VOIP & Traditional telephony system)? Why we use this feature? what problems shall we face if we don't use '9' before making ...
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1answer
2k views

Difference between sip proxy and sip outbound proxy? [closed]

What is the basic difference between a sip proxy and a sip outbound proxy. Can sip proxy and outbound proxy be the same?
2
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2answers
374 views

Splitting Data and Voice by creating GRE tunnel for Data, using overhead for Voice

A client: 3 sites with L2 links to our Data Centre. I create L3 links by providing IP's both sides. I want to create a GRE tunnel over each link with seperate IPs in order to route Data over these new ...
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1answer
139 views

Auto-Attendant on Cisco CUC

I'm trying to apply an auto-attendant on a CUC, where the voice message will be just played for one time and stops, and if the caller didn't dial anything the call would hangup after 10 sec. I know ...
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2answers
1k views

CISCO CUBE is as SBC suitable for ISP

I am currently planning a voice network and test different ways. Currently a classic IP network with various Cisco Routers is used to bound different media (fiber, copper, MPLS) and route to a classic ...
3
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3answers
376 views

Understanding of NAT and VoIP [closed]

I need some help to better understand how networks work, ports, and communication. Suppose we have this situation: We have on the left a corporate network (let's call it "A") which has a DMZ with a ...
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3answers
938 views

LAN QoS for VoIP

Is LAN QoS required for VoIP applications? We have basic network infrastructure: PC (Softphone) -GigEth-> [Switch] -GigEth-> [Router/Firewall] -> Internet (100 Mbps) -> [ITSP] Voice ...
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1answer
176 views

FXO to GSM routing

I am new to VoIP so apologize if this is a dump question I want to accept a traditional telephone call (FXO) channel and based on the callers extension selection I want to switch the call to set of ...
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1answer
636 views

Optimize WiFi router settings for VoIP

Is there a quick way how to optimize Wi-Fi AP/router settings for better VoIP performance? I use SIP protocol. Can I tweak RTS or fragmentation threshold values for better voice performance? I am ...
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2answers
86 views

Which header is added to the voice data payload in Layer-2 when we use an IPsec VPN?

According to this link, Planning and Design, an encrypted IPsec voice data packet contains: IPsec header, ESP header, GRE IP header, IP header, UDP header, RTP header. Which header is added in Layer-...
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1answer
612 views

Realtime Transfer Protocol (RTP) belongs to which layer of OSI?

Real-time Transfer Protocol (RTP) belongs to which layer of OSI? Various people said various things from transport-layer to application-layer.
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1answer
75 views

When voice data is transmitted over the Internet, does session layer add any header to the packet?

For voice data, session layer use SIP, H.323, MGCP, H.248, etc protocols. Do these protocols add any header to the voice data payload? When voice data is transmitted over the Internet, does session ...
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1answer
162 views

How many headers are attached to voice data when we use VoIP services? [closed]

How many headers are attached to voice data when we use VoIP services? What I understand is, the maximum number of headers that can be attached to voice data is 4. For example, Layer-2 would add a ...
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1answer
86 views

How can I see if this line is an isdn30 line?

I got an port here from somewhere, and I'm guessing its an isdn30 line but I'm not sure. How can I check if its indeed an isdn30 line? I can plug my laptop in with an utp-cable but is there a program ...
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2answers
5k views

Can't configure the Cisco CP-8851 IP Phone

I do not have a cisco contract or license, but I did order the Cisco CP-8851 IP Phone from Amazon, and was hoping that I could configure it to work with my VoIP SIP PBX. But I can't seem to log into ...
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1answer
120 views

“gateway to gateway link” in VoIP?

I want to route some calls to my VoIP number a call center overseas. The call center is telling me that I need to do a "gateway to gateway link" in order to make this happen. I'm not exactly sure what ...
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0answers
70 views

Issue with voice performance between two ip phones at the same site connecting to two different CUCM?

I have one branch which is (branch-1) with two groups of ip phones, one group is connecting to CUCM-1 in HQ and the other group is connecting to CUCM-2 in the branch (branch-1) and the connectivity ...
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2answers
401 views

VLANs isolating networks (VoIP/Wi-Fi)

I have to set up our network in our new office. I'm no networking expert (developer), but I need some input and advice here for some things I wonder about. I have purchased the following: 2 x Cisco ...
5
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1answer
287 views

VoIP QoS over DIA/L3VPN physical circuit

This Q. is really confirmation to what I already suspect. On a single physical interface with a carrier that uses two dot1q logical sub interfaces to handle DIA and L3VPN, I suspect any usage of DIA ...
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3answers
10k views

How is it possible to run VoIP on CAT3. Do you not need CAT5 for the voice data?

So I never knew this till today but I thought you needed CAT5 for VoIP but this business is running VoIP on CAT3. Don't you need the extra wires for the voice, data and power?
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3answers
457 views

What is the exact engineering involved behind creating a SIP trunk for any customer?

When a company is setting up a PBX and wants to use a SIP trunk, why does it have to buy it? Is there no way to provide itself with one on its own?
3
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1answer
217 views

dmz and ip-phone on medium network

Hi I'm trying to sketch a computer network. The network include about 50 computers for employees, 20 computers for tech office, a few network printers, a wifi area and every employee has an ipPhone. ...
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1answer
113 views

Is wireless network sutabile for VoIP services? [closed]

We are moving our HQ to a new building, I am responsible for designing the network and the data center, I was thinking to make it all wireless, but what about the voice services, can we get a good ...
0
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1answer
703 views

Cell-phones and protocol-stack [closed]

When making a phone-call these day - the datastream is divided into packages, isnt it? But which protocol-stack is used then? VOIP is using tcp-ip but but what about cell-phones? For instance - the ...
4
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1answer
15k views

Converting PCAP to WAV

How would I go about converting a RTP stream from a pcap file to wav format with a command-line tool such as sox?
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1answer
12k views

Correct ACL rule to open UDP ports for VoIP

I have the current rules in an attempt to open port 5060 and 10000-20000 for my VoIP provider. We are on a Cisco 1921 router. This ACL is applied to the WAN port on the router facing the ISP. Nmap ...
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1answer
108 views

Toshiba Strata CIX Calls From 'cisco' [closed]

We have a Toshiba Strata VOIP phone system. Getting bombarded with calls from 'cisco'. Answering the call immediately hangs up. Happening every 3-4 seconds. Not sure if they are originating from ...
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1answer
504 views

Downstream QoS Feasibility

I work for a VoIP provider, and one of the biggest hassles I deal with is downstream traffic management. Our flagship product is QoS-enabled bonded T1 or SHDSL bundles configured to support our own ...
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1answer
287 views

Why is it necessary to pay for VOIP calls to phones?

I'd like to start by apologizing for not doing a thorough research on this subject, but after talking to a work mate VOIP came up. I know very roughly how it works (most basic knowledge you can ...
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3answers
24k views

CUCM 10.5 - Reset Admin name & password

I need to reset my CUCM Admin password and name. On previous versions of Cisco Call Manager, I had to log in to CLI and run these commands : utils reset_ui_administrator_name utils ...
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2answers
982 views

Troubleshooting One Way Audio

Quick question for the VoIP gurus. A while back I learned a trick where if I received a call on a VoIP phone, but after answering I couldn't hear anything, I would ask the person to press a number on ...
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1answer
5k views

Double-NAT's Effects on SIP and RTP

What effects does double-NAT have on VoIP? What happens to the traffic in this type of situation and what conditions can occur as a result of it?
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2answers
1k views

IP Phones causing printing issue

Background We have Mitel IP phones. The phones use dhcp option 125 to get configuration information, and this tells them to use 802.11q tags for vlan id #5, with address range 192.168.16.0/24. Our ...
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1answer
657 views

Can I Use Different Versions of CME and CUE

I am running CME 8.6 on a Cisco 2811. I would like to install NM-CUE and run CUE 7 with this. It this possible, even with a version mismatch?
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2answers
182 views

Echo on VoIP Calls

We use Ring Central for VoIP. I inherited this company and so that's the service we have, and I know nothing about VoIP. We have increased our bandwidth to 80Mb down and 6+Mb up, and that's as high ...
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2answers
1k views

rtp connection with nat

Consider server S with some public ip and client C behind NAT N. Now C sends some messages on a UDP channel to S. Client C declares the port to which S should connect the RTP stream. As you might ...
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5answers
13k views

Connect a POE VoIP phone to a non-POE Switch

I'm working on a project where I need to make a network for all PCs in the site. I need about 8 Ethernet sockets in each office of the site. I found that there's already two Ethernet sockets in each ...
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1answer
1k views

Use a Switch or Router for PoE on VOIP system

I have a question regarding if a switch or router is the way to go in my situation. We have a modem through Comcast that only has one available port on it right now and we are getting a VOIP system ...