Are our public IPs shared?

[blueyonder-user]

Hi, just a general question about our public IP addresses, are they shared between customers?

I thought our IPs are dynamic so you might get a different one every so often, but thought they'd be unique for each customer.

Anyone know if this assumption is correct?

Thanks

[Client62]

Our Public IP & customer host name have not changed in at least 5 years,
however it is a dynamic IP and could change without warning.

To see the customer host name : nslookup <Public IP>

[nodrogd]

Two things will possibly change it:

1) Having a hub replaced. Just had mine replaced & after 7 years I now have a different IP.

2) A change of CMTS allocation at the headend.

[blueyonder-user]

Thanks @Client62 & @nodrogd

I get that our IPs might change over time, but is it unique? As in only one customer can have a particular IP at a time?

[Tudor]

Yes. The internet would not work if it was shared. That’s why we are running out of IP v4 addresses. 

[gitty]

I think the OP means carrier grade NAT, where many customers access the internet through the same public ip.

[carl_pearce]

VM do not use CGNAT or MAP-T, so you do not 'share' your public IP address with other customers.

[ravenstar68]

No, they are not shared.  VM did trial IPv6 using dual stack lite prior to covid, that would have meant effectively that IPv4 was using CGNAT.  The fact that VM didn't roll it out nationwide should speak volumes as to how well that worked out.

[ravenstar68]

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@Tudor wrote:

Yes. The internet would not work if it was shared. That’s why we are running out of IP v4 addresses. 

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The main internet registries ran out of IPv4 addresses to allocate over a decade ago.  The fact that companies like Virgin Media still have IPv4 addresses to use demonstrates how wasteful the allocation was. 

[Tudor]

@ravenstar68 said "The fact that VM didn't roll it out nationwide should speak volumes as to how well that worked out." Surprising as a lot of thing from VM do not work very well!