any dangers of filtering every /24 on full internet table to preserve FIB space ?

Mon Oct 10 17:23:44 UTC 2022

Heho,
Let alone $all the /24 assigned under the RIPE waiting list policy.

In the Geoff Huston spirit, I quickly took a look how less specifics for /24s looks in my table:

8 {'no_less_specific': 16, 'has_less_specific': 0, 'sum': 16, 'least_specific_length': {}}
9 {'no_less_specific': 9, 'has_less_specific': 4, 'sum': 13, 'least_specific_length': {'8': 4}}
10 {'no_less_specific': 38, 'has_less_specific': 0, 'sum': 38, 'least_specific_length': {}}
11 {'no_less_specific': 98, 'has_less_specific': 4, 'sum': 102, 'least_specific_length': {'10': 4}}
12 {'no_less_specific': 269, 'has_less_specific': 31, 'sum': 300, 'least_specific_length': {'9': 5, '11': 23, '8': 1, '10': 2}}
13 {'no_less_specific': 490, 'has_less_specific': 98, 'sum': 588, 'least_specific_length': {'11': 46, '8': 2, '12': 48, '10': 2}}
14 {'no_less_specific': 1022, 'has_less_specific': 188, 'sum': 1210, 'least_specific_length': {'13': 99, '8': 4, '12': 44, '11': 33, '10': 8}}
15 {'no_less_specific': 1641, 'has_less_specific': 476, 'sum': 2117, 'least_specific_length': {'14': 210, '13': 95, '12': 87, '11': 37, '8': 21, '9': 3, '10': 23}}
16 {'no_less_specific': 10319, 'has_less_specific': 3286, 'sum': 13605, 'least_specific_length': {'15': 577, '14': 527, '12': 470, '13': 548, '9': 14, '11': 446, '8': 173, '10': 531}}
17 {'no_less_specific': 4474, 'has_less_specific': 3942, 'sum': 8416, 'least_specific_length': {'16': 1816, '14': 536, '12': 276, '13': 343, '8': 44, '15': 324, '9': 4, '10': 181, '11': 418}}
18 {'no_less_specific': 6926, 'has_less_specific': 7179, 'sum': 14105, 'least_specific_length': {'17': 888, '14': 1367, '16': 2394, '15': 776, '12': 289, '13': 487, '9': 15, '11': 514, '8': 108, '10': 341}}
19 {'no_less_specific': 15056, 'has_less_specific': 10151, 'sum': 25207, 'least_specific_length': {'17': 813, '16': 2561, '15': 1113, '13': 758, '14': 1373, '12': 544, '18': 1213, '8': 198, '9': 28, '11': 770, '10': 780}}
20 {'no_less_specific': 19592, 'has_less_specific': 24430, 'sum': 44022, 'least_specific_length': {'17': 1319, '14': 3435, '16': 6868, '12': 1216, '11': 1568, '13': 2221, '15': 1919, '18': 1450, '19': 2465, '9': 45, '8': 374, '10': 1550}}
21 {'no_less_specific': 22889, 'has_less_specific': 30065, 'sum': 52954, 'least_specific_length': {'17': 1886, '16': 5234, '14': 2569, '13': 1346, '19': 5019, '18': 1717, '12': 2011, '9': 78, '20': 3210, '15': 1760, '8': 513, '11': 3001, '10': 1721}}
22 {'no_less_specific': 59137, 'has_less_specific': 51280, 'sum': 110417, 'least_specific_length': {'17': 3787, '16': 10049, '13': 5469, '19': 4100, '14': 3784, '21': 3287, '18': 3128, '11': 2965, '12': 3428, '20': 4152, '15': 3157, '8': 1018, '9': 166, '10': 2790}}
23 {'no_less_specific': 41052, 'has_less_specific': 60043, 'sum': 101095, 'least_specific_length': {'17': 3844, '21': 3382, '14': 3324, '16': 10032, '22': 13207, '19': 5658, '15': 3007, '18': 2973, '11': 2243, '13': 1645, '12': 1752, '9': 277, '20': 4941, '8': 1260, '10': 2498}}
24 {'no_less_specific': 257032, 'has_less_specific': 295714, 'sum': 552746, 'least_specific_length': {'22': 38330, '17': 19319, '16': 51487, '21': 16799, '23': 14813, '13': 10067, '14': 14328, '20': 26634, '18': 19216, '12': 9440, '11': 10001, '15': 14437, '9': 2700, '19': 31119, '10': 7992, '8': 9032}}

So it seems like there is a healthy amount (~260k) prefixes which lack a less specific.

With best regards,
Tobias

-----Original Message-----
From: NANOG <nanog-bounces+tobias=reads-this-mailinglist.com at nanog.org> On Behalf Of Stephane Bortzmeyer
Sent: Monday, 10 October 2022 17:21
To: Edvinas Kairys <edvinas.email at gmail.com>
Cc: NANOG Operators' Group <nanog at nanog.org>
Subject: Re: any dangers of filtering every /24 on full internet table to preserve FIB space ?

On Mon, Oct 10, 2022 at 05:58:45PM +0300,  Edvinas Kairys <edvinas.email at gmail.com> wrote  a message of 35 lines which said:

> But theoretically every filtered /24 could be routed via smaller 
> prefix /23 /22 /21 or etc.

I don't think this is true, even in theory, specially for legacy prefixes. There is probably somewhere a Geoff Huston survey on /24 without a covering route.