Why various result of external IP address within same location.

Visited a client site and ran various ‘my ip address’ site to determine what is the External IP address the provider assigned.  Noticed that each device resulted a different value.  For example their phone and their tablet gave different values where that last segment changed (xxx.xxx.xxx.19 and xxx.xxx.xxx.20), yet when we ran myipaddress in our device gave a whole different value in all segments.

We understand that the internet provider assign the cable modem or location a single dynamic external ip.  The location router managed a total different internal ip sequence values and assigns it to each device connecting to the wifi or router within the location.  Thus the cable modem has 1 IP address and the devices within the location has different ip address.

Why would the “my IP address” website display different IP address in all devices connected to the same wifi?
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KimputerIT ManagerCommented:
The provider probably can answer this the best. Could be that the router is more IP assigned (without you knowing it, if custom router software didn't reveal it to you). If you didn't install a router yourself (bridged mode), you probably have no control over it.
janaAuthor Commented:
I thought all these website that retrieve your device IP address, like http://www.myipaddress.com and http://whatismyipaddress.com, returns the actual external IP assigned by the internet provider not the office router.  

Did I understand correctly?
KimputerIT ManagerCommented:
Those websites are designed to return the external IP address assigned by your ISP (consumer connections return only one IP address).
In some cases, bigger offices have a modem in bridged mode, whereby the (usually more expensive) office router takes the assigned IP address(es). Hence, if you requested the ISP to give you MORE IP ADDRESSES, AND you configured it correctly in your office router (in a round robin fashion), those websites will return several results (those being the addresses you configured) with every refresh.

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janaAuthor Commented:
The client was bewildered as well when we checked their IP via myipaddress and the diferente results.  They are not a big office and they don’t have an IT dept.  I asked them what kind of internet setup they have with their provider  (cable, DSL, fiber, satélite) and they don’t know.

They want to know why different IP, so going to call their provider and see - just by asking if they are supplying more IP would be enough question to check out your observation? Or what can we ask the ISP?
KimputerIT ManagerCommented:
Yes you can ask your ISP, but ONLY if those IP's are close to each other (as you said, x.19 and x.20). Tell them you are exploring clients network situation and wonder what the 2 IP addresses are. Those are either yours (and the modem/router decided to use them), or they could be shared in some way (with other ISP subscribers).
If the IP numbers were REALLY REALLY different and REALLY A LOT of results, you might want to check out if you have some sort of VPN/Proxy situation going on.
janaAuthor Commented:
Last question, would the different IP be cause by the ISP internet setup being fiber rather than cable?
KimputerIT ManagerCommented:
Material has no influence on how an IPv4 connection works. They're both just transporting packets from one end to the other, and the underlying protocol is the same.
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