I hear often that it is hard to practice/demo voice related configurations with GNS3. This is only partially true.
It is correct that GNS3 cannot substitute Multiservice routers like 28xx etc because the DSP resources cannot be emulated. For using T1/E1 or FXS/FXO connections you need the real hardware interfaces and of course another PBX/router interface to connect your T1 to. If you have a double T1 you could use a T1 x-over to let the router do both ends.
For all other configurations like Dial-peers, translation patterns, SIP-UA configurations, CME, ephone registrations, CUBE etc, GNS3 can do the job. Just an example from my own lab: I have several accounts at SIP-Providers in US and Europe to use with a standard sip-phone like X-Lite. The router can log in this SIP-account and let CME or UCM handle the call. Via this way I provide a local german PSTN-number for my german friends which makes my phones in Minnesota ring. The thing has of course a downside… they keep forgetting that I am 7h behind, but for this purpose Unity will take the call.
Where is GNS3 now coming into the ballpark? For each router you can specify only one SIP-registrar server, but I like to have all my SIP-accounts registered at the same time to route calls between them. GNS3 can now run the virtual routers, one for each SIP-provider, register your PSTN-numbers and UCM/CME can do the call handling.
by Patrick Geschwindner, Ascolta
There is a post going into more detail how to setup GNS3 and make it actually talk to another (physical) router outside of your PC and if you like to the internet. The article is called: GNS3 setup and outside connections.
If anyone is considering teaching themselves voice with minimal to no prior experience in voice my advice is that it can’t be done without great effort.
My recommendation is that after teaching myself CCNP (and I do feel I really learned the curriculum not just how to pass the test) I don’t believe it is possible to teach oneself CCNP voice (CCVP). Voice is complicated. Call Manager is super complicated, like about 5 times more complicated than any IOS configuration I have ever seen. Since that is the case and most community colleges don’t have good voice programs your options are limited. Either get on the job training or enroll at a school like Koenig-solutions. If you don’t want to shell out 10,000 dollars to learn voice at a boot camp I would say just memorize all of the dumps and pass the tests. You may know little to nothing but with the certification you can get a job in voice and learn it on the job.
And before I came here I already had Call Manager VM wares and was considering building my own lab. But even 1,300 dollars would not be enough money to build yourself a lab since as stated above “GNS3 cannot substitute Multiservice routers like 28xx etc due to the fact that DSP resources cannot be emulated. Plus remember that for using T1/E1 or FXS/FXO connections you need the real hardware interfaces and of course another PBX/router interface to connect your T1 to.”
Plus when you have problems you won’t have a clue how to make it work or troubleshoot. For a point of reference my instructor has spent almost two hours troubleshooting 3 of my labs that were not working and he is almost a CCIE voice. I mean forget it really its insanely complicated. Like so much so that after a while of trying to take notes on the step by step procedures in order to get something to work in CUCM I just gave up and started to record the screen with camtasia because I couldn’t retrace my steps based upon written notes.
But I recorded about half of my CUCM labs which is nice… I am not sure if I will be reviewing all of those videos or what but at least I have them. So my advice, voice is a completely different animal its nothing like CCNA, CCNP or even CCSP (security). So get trained on the job, or at a bootcamp or save your sanity!