The minimum number of IP addresses an autonomous system can have
bgpservice-provider
Is it possible to have an autonomous system with just one IP address?
Best Answer
Is it possible to have an autonomous system with just one IP address?
Theoretically, yes, but the ISPs will not advertise any IPv4 prefix larger than /24 or IPv6 prefix larger than /48 on the public Internet. You could certainly have that inside your own network or with another company or ISP, but it will not work on the Internet.
Also, the AS concept is really decoupled from the IP addressing concept. You could certainly set up a transit AS between two other ASes and use only private addresses, or one or two public addresses without advertising any of your addressing because only the two ASes for which you are providing transit services need to know only your directly connected addresses and not advertise them.
That means you could have an AS with no public addresses. The AS and its addressing do not necessarily directly relate.
There is no tunneling. This is completely normal. With IP routing you are concerned about the source and destination address which doesn't change unless something is NAT'd. If a router in the middle has an RFC1918 address that's fine as it can still forward transit traffic as again the source and destination is unchanged.
Each router will simply reply to the source with their own directly connected interface address. The 10.14.0.1 above is not being routed over the internet, it's simply the device that is attached to the CPE on the WAN side.
There is no magic technology being used. It's pure standard routing.
This question is akin to asking, "Why can't I use a screwdriver to hammer nails?"
You could use OSPF in certain inter-AS situations if you REALLY, REALLY wanted to/needed to. There would be many "gotchas" and caveats to keep in mind when utilizing OSPF as an EGP.
Just like you could hammer nails with a screwdriver. However, you would risk breaking the screwdriver, harming yourself, etc.
You could do it, but why would you? There is a perfectly usable/heavily implemented routing protocol created for inter-AS communication, BGP. Why attempt to utilize OSPF for an undesigned purpose?
Best Answer
Theoretically, yes, but the ISPs will not advertise any IPv4 prefix larger than /24 or IPv6 prefix larger than /48 on the public Internet. You could certainly have that inside your own network or with another company or ISP, but it will not work on the Internet.
Also, the AS concept is really decoupled from the IP addressing concept. You could certainly set up a transit AS between two other ASes and use only private addresses, or one or two public addresses without advertising any of your addressing because only the two ASes for which you are providing transit services need to know only your directly connected addresses and not advertise them.
That means you could have an AS with no public addresses. The AS and its addressing do not necessarily directly relate.