Re: "Tactical" /24 announcements

[Sabri Berisha <sabri () cluecentral net>]

----- On Aug 9, 2021, at 9:22 AM, Masataka Ohta mohta () necom830 hpcl titech ac jp wrote:

Hi,

> It should be 14M.

Just for fun, I did the math. A total of 16,777,216 /24s fit in 32 bits. Take away all the reserved space as per IANA 
(this is 1,266,696 /24s, see below), and we end up with 16,777,216 - 1,266,696 = 15,510,520 potential /24 
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The largest FIB table I have seen (hi Jim!) was 3,563,546 routes in hardware. This was in a lab environment, of course.

Thanks,

Sabri


https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml 
Subnet          Number of /24s
        
0.0.0.0/8       65536
10.0.0.0/8      65536
100.64.0.0/10   16384
127.0.0.0/8     65536
169.254.0.0/16  256
172.16.0.0/12   4096
192.0.0.0/24    1
192.0.2.0/24    1
192.31.196.0/24 1
192.52.193.0/24 1
192.88.99.0/24  1
192.168.0.0/16  256
192.175.48.0/24 1
198.18.0.0/15   512
198.51.100.0/24 1
203.0.113.0/24  1
240.0.0.0/4     1048576
        
Total reserved  1,266,696