"What Happens When the Internet Goes Down?"

I didn’t really know where to place this, but a lot of clients have started asking me about this. Usually I just tell them to get another line, just in case, but I’m pretty sure there’s a better solution to that. What are some solutions that I can provide clients that enables them to still be able to have partial to full access or their system if there is no internet.


Usually you would setup some analog lines.

Then again I am not sure what you mean. Are you talking about outbound calling or internal calling?

Personally I think there are many ways to do “redundancy” and maintain uptime.

To start, FreePBX/Asterisk can use SIP trunking, PRI lines, analog POTS lines, and probably other types of services I don’t know about. However PRI/POTS lines require extra devices to be put into the equation and add cost. You can get external boxes or internal cards. Digium, Rhino, and Sangoma are the popular names I know about for these parts.
[Analog Cards][1]
[Digital Cards][2]
[VoIP Gateways][3] (external)
If the internet goes down then a PRI or POTS line would still be up. However don’t think that these aren’t without failure. I’ve read people having problems with PRI in the past. But these systems have experiences many years of hardening that has made them very resilient. Personally, I don’t like this method of redundancy.

What I like is building redundancy at the Internet Service Provider (ISP) and SIP Trunking provider. SIP trunking can be delivered on anything. DSL, T1 (essentially to PRI at that point), Cable, Fiber, DIA (dedicated internet access), and so on. I hate T1 (old, slow, and expensive). Business Internet from Companies like Comcast or Verizon FiOS can work really well just be aware of lack of QoS once packets leave the LAN and potential issues if you aren’t in the greatest locations for service. DIA, Metro Ethernet, and those types of connections are the best with SLA agreements for uptime and repair and guaranteed speed and quality (jitter, latency, etc) however they cost a LOT more and if you only have one connection you are still at the mercy of 1 provider.

So here is what I like to do. If available in your area, get Verizon FiOS. I find they have great speed, low latency (Fiber), and awesome uptime (at least around my area). Then get a backup ISP like Comcast Cable or anything you can get for “cheap”. Get a router that does load balancing and failover. If one ISP goes down traffic will redirect to the other ISP. I like Ubiquiti EdgeRouter, PFSense, or Mikrotik for cost reasons but most business grade routers can do this (Cisco, Sonicwall). It is very unlikely that both ISP’s will go down at once. Then have a few SIP trunking providers with a per minute rate and setup some routing. If a provider goes down, you have others. Add in PoE switches and have everything hooked to a UPS system and you can have a phone system that stays online in pretty much any situation. You could even go further with two FreePBX systems linked over a VPN between two sites for offsite disaster recovery. And from what I’ve seen this can all be done for less money, be more resilient, and be more flexible then traditional systems.

Hope this helps.
[1]: http://www.digium.com/en/products/telephony-cards/analog
[2]: http://www.digium.com/en/products/telephony-cards/digital
[3]: http://www.digium.com/en/products/voip-gateway


I suggest you look into a real SIP proxy cluster with BGP in place for failsafe Inbound calls, in the absence of your Asterisk endpoints availability inbound calls can be routed to secondary numbers (cell phones maybe), For outbound calls at the lowest level you will need a multihomed, failover safe replicated Asterisk/FreePBX HA network solution at your core (or the same proxy cluster working the other way to which your extentions register to) if you care to add TDM/Analog PSTN service that will also need to be failover safe to your clients, either at the CO level or also with redundant hardware, if you have “hosted” clients, then you they are pretty will SOL when they loose connectivity to your NOC apart from a good old fashioned SLT “under the stairs” :slight_smile:

Thanks for the response. I usually tell them to get a simple analog line but they usually respond with, then why don’t I just get all my lines as analog lines? I would say both internal and outbound calling would be needed if internet were to go out.

Often a single pots line for fax/alarm panel makes sense. Add a SPA 3100 series.

Tell them ii is for SRST.

Hi Jay!

Thank you so much for breaking this down for me, I really appreciate it! I would definitely consider getting a second provider for bigger clients, in fact I know that they would appreciate that type of redundancy. However, how would this work on a client that doesn’t have the budget for two internet lines? Or a client that doesn’t have an on premises PBX. Is it possible to have a client who only has one line on one phone with only one internet line have some form of redundancy?

Thank you once again for your reply! It has given me alot to think and ponder about!

Depending on where you get your DID, there is might be bit of redundancy there… My home FreePBX is as small of a user base as possible. Me… one number… two phones.

My provider has ability to forward to either a phone number or send to voicemail if no response. I have a recording stating “we are not available, please try later” on the voicemail. This works fine for small installations with a small number of numbers. If you don’t have a backup plan for outages, people will get the fast busy (no such number) type message (of course, once again, depending on your DID provider).

There are lots of offices that need the more elegant dual internet solutions mentioned above - especially if continuous Internet access, not just phone service, is the concern.

However "brk"s solution works great for a couple of our customers. One 9 extension office has calls route to their cell numbers. The other with 14 extensions just goes straight to voicemail and then they get an email notice. It happens rarely so spending more money is not worth it to them

We’ve another customer that started out with 4 POTS lines. To increase capacity when they occasionally need it we added a per-minute VOIP trunk. This “just worked” for outbound calls. For inbound calls the POTS line provider has a setting for forwarding calls to a specified number if either all of your POTS lines are in use or the POTS line connection to your office is not available. You could theoretically drop down to 1 POTS line - they just are not comfortable doing that yet. So they can get calls (in most situations) if either their Internet or POTS lines are down.


As I am sure you knew to begin with, and have since been reminded, there are a thousand different ways to do this, and no one solution will be right for every installation/client. Depending on what is most important (incoming calls from clients vs intra-company calls among developers, vs outbound 911, etc) and what sort of budget is available, all sorts of different solutions will arise.

What the proper response is also depends on the location of the PBX (solutions for hosted sites will be different than for on-site machines) and the geographic location of the PBX. For example, the likelihood that FIOS and Comcast would both go down at the same time in a major metropolitan area is far different than the likelihood of that happening in a more rural area. For example: we once had a car hit a telephone pole a mile down the road and lost power, phones, AND internet: that would never happen in an urban environment (barring major disasters).

Our solution for the central office is a machine that is located on-site (so the bulk of our employees do not count on internet for their phones). Almost all calls come in on a PRI. If this circuit is down (PBX crashes, extended power failure, provider problems), it fails over to an ITSP. If the ITSP cannot reach the PBX, it fails over to my cell phone. I don’t like to rely on an ITSP for our primary voice traffic, as it is only as good as our internet connection, which is simply not as good as a nice, old-fashioned, expensive T1/PRI. Having said that, I can justify the cost based on the amount of voice traffic we see, plus the fact that we are, quite simply, OUT OF BUSINESS if our phones are down, more so than other companies might be.

Branch offices have analog phones on their desks, in addition to their SIP phones. This is because the internet/IPSec connection to the central FreePBX machine just isn’t reliable enough for my liking. I have often considered putting a PBX in each office and routing the analog lines through them via a second line appearance on the SIP phones, but the idea of administering a dozen more PBXs has put me off of that solution for now.

More than anything, I would counsel that you sit down with each client and “have the talk” about redundancy. Explain what could go wrong, what would happen if it did, what the options are to avoid it, and how much it costs. From there, find out what their priorities are and help them craft a solution. As a bonus, by involving them it will be harder for them to blame you when the corner they chose to cut comes back to bite them.

Good luck, and let us know what you find,


PS: As for “Why don’t I use POTS for all of my lines?” Well, the answer is additional hardware cost, plus ongoing charges from the phone company. On the other hand, there is nothing wrong with a FreePBX box that has 1-15+ analog lines connected via a SIP gateway, PCI card, or Xorcom Astribank. That’s not the right solution for everyone, but it might be perfect for some.

this is the reason we opted for hosted solution. since we have multiple satellite offices we needed something colocated because if the internet goes down there go the phones as well. in some sat offices we do implement redundant ISP only if they’re ok with the additional cost. the company does utilize answering service so in case of longer outage we use that. but then again in metro areas outages are not frequent and even if there are any hiccups they get resolved pretty quickly.