How ISP connect each other?

Question

So my home internet router outside interface have an IP 158.x.x.137 and 158.x.x.129 as default gateway which is /25 network, and the inside interface have an IP 192.168.1.1 which is the default gateway itself (my home LAN /24).

If my understanding is correct then the entire 158.x.x.128/25 is all of the customer of my ISP right? I can ping all of them under 2ms (basically my neighbor). So all of us is under the same switch connected to the inside interface of my ISP router (158.x.x.129) right?

Then what the outside interface of my ISP router connected to? I meant the inside interface have already a public route able IP address. Is it the same address on both end? And also obviously they have more than 128 customer, how they connect that?

In: 3

Answer 1

first, a very very basic understanding you have is correct.

but it can be fragmented more.

each IP range can have vlans aswell.

so Connecting from telstra to Optus is quite simple, they are given a vlan ID.
they then just route the traffic through their IP ranges.

eg

aus to America may go
1.1.1.1 – 2.3.2.3.

now the traffic is in murica.

the routing is done at the other end either via a router, switch.
each of these companies may have their or others networks they use.

for example.

tracert 1.1.1.1 gives me 6 hops.

but tracert 236.25.127.99 gives me 31 hops.

I advise you watch a video on corporate interconnect networks.

or IT network infrastructure diagram