Ping router

[AndyChr_2274538]

Hi

Is it possible to ping a $g router that has a smarty sim in ?

Router is connected to internet and has correct APN, can browse etc, have enabled respond to ping on WAN interface and even tested with firewall disabled but I cannot get a response to a ping.  
Thanks

[SmartyTrousers]

No it isn't. In common with most other mobile networks, Smarty uses CG-NAT (carrier-grade network address translation) meaning you share an external IP address with other users, and it is not possible to make an incoming connection to your router from the internet.

The only UK mobile network which allows you to do this is Three, using the 3internet APN (note that if you set that APN on Smarty, you may get internet connectivity but your connection will still be CG-NAT-ed).

Depending on what you are trying to achieve, you may be able to use a workaround, for example, a service like Tailscale or ZeroTier. If you are wanting to run a web server on the standard ports you could use a Cloudflare tunnel.

[sen101]

Oh botheration.  Is there no way around this?  I just subscribed to SMARTY to use as a backup internet service but if I can't get a publicly routable IP address it's useless to me.

What should I do?  Just throw the SIM in the bin when it arrives and not activate it? 

[SmartyTrousers]

Yes, there are a few workarounds - they are right at the end of my post.

If you want to cancel and you've already paid for a month of service then you'll want to leave the SIM unactivated and start a web chat with Smarty support to ask for a refund.

If you've ordered a SIM without having already paid for a month of service, yeah, you can just bin it.

[sen101]

Not familiar with TailScale or Zero Tier.  

Essentially I run several services on my home network that I need to access externally, there are a few web services (OpenWISP, Home Assistant, Unifi Console) then also I have several VPN end-points that devices on the web connect back to, (these are network devices that I manage for a couple of local charities).  These are currently all setup to use DDNS via AWS Route53.  So I don't need a static IP, just a public one.

Will TailScale work for that?  How do I enable it?

[SmartyTrousers]

Tailscale and ZeroTier basically enable you to create a VPN without needing to worry about the networking side of things - their client software (basically a virtual network adaptor) will automatically find a route between the devices you are wanting to connect, resorting to routing it via their own servers if a peer to peer connection is not possible.

The downside is that you need their client software installed on any devices you want to connect, so I don't know whether that would work for your use cases or not.

You could always give Smarty plus ZeroTier or Tailscale a go, and if it doesn't work for you, you're not tied in at all and can just turn off auto renewal of your plan.

If the above doesn't work for you, one option might be what I use for my home broadband - a Three ScanCom SIM from Amazon. This is a SIM which you pay a lump sum for up front for a set number of months of service with a set amount of data each month (unlimited, in my case). Once the period is up the SIM will automatically be disconnected.

[sen101]

Interesting, I've never heard of anything like the ScanCom SIM before.  Is it legitimate?!  Seems weird that they have these arbitrary expiry dates on the SIM cards, are they using some sort of loophole?

Assume it has to be a '3' card due to what you said about 3 being the only provide who give public IPs on the mobile APN.  Is this contractually part of the service they offer, or in theory could they switch to CG-NAT at any point and you'd be S.O.L.?

[SmartyTrousers]

@sen101 Yeah, it's legit. ScanCom have been around for decades and are authorised resellers of Three (and the other networks they sell SIMs for). ScanCom have basically taken out a number of contracts with the networks which end on specific dates, hence the arbitrary expiry dates of the SIMs. ScanCom lower the prices of the SIMs every now and again as the amount of service left on them dwindles. Your contract is with ScanCom rather than the network, so any support requests need to go to them.

You are right that you would need to get one of their Three SIM cards and use the 3internet APN for a public IP address.

You raise a good point, and it's something that crossed my mind recently with the announcement that Three and Vodafone have got the go-ahead to merge. I don't think the public IP is part of the contract, and in theory that might disappear when Three and Vodafone merge their systems. It wouldn't personally affect anything I do, but it's something to be mindful of.