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

[Brandon Martin]

On 10/20/22 17:50, Adam Thompson wrote:

Alternately, a valid technique is to have a default route AND a partial BGP 
feed (a filtered full feed is by definition a partial feed).  That helps 
optimize outbound routing a little bit, you still get the advantage - mostly - 
of multiple inbound carriers; but you still have to pick one carrier to do the 
heavy lifting for you.  And you are paying them to route for you, so that's not 
an unfair shifting of the routing burden, unlike relying on covering routes.  
Note that this approach does NOT provide any redundancy, unlike having full BGP 
feeds.


As a note, you can get redundancy (but still none of the best-path 
advantages of having multiple transits) by asking your transits to 
originate default in their BGP feed and then selectively accepting it. 
You can either ECMP it or pick priority with localpref.


You need multiple full-view transits for this to work, though.

--
Brandon Martin

Weekly Global IPv4 Routing Table Report

[Routing Table Analysis Role Account]

This is an automated weekly mailing describing the state of the Global
IPv4 Routing Table as seen from APNIC's router in Japan.

The posting is sent to APOPS, NANOG, AfNOG, SANOG, PacNOG, SAFNOG
TZNOG, MENOG, BJNOG, SDNOG, CMNOG, LACNOG and the RIPE Routing WG.

Daily listings are sent to bgp-st...@lists.apnic.net.

For historical data, please see https://thyme.apnic.net.

If you have any comments please contact Philip Smith .

IPv4 Routing Table Report   04:00 +10GMT Sat 22 Oct, 2022

  BGP Table (Global) as seen in Japan.

Report Website: https://thyme.apnic.net
Detailed Analysis:  https://thyme.apnic.net/current/

Analysis Summary


BGP routing table entries examined:  913066
Prefixes after maximum aggregation (per Origin AS):  344590
Deaggregation factor:  2.65
Unique aggregates announced (without unneeded subnets):  440326
Total ASes present in the Internet Routing Table: 73756
Prefixes per ASN: 12.38
Origin-only ASes present in the Internet Routing Table:   63346
Origin ASes announcing only one prefix:   25997
Transit ASes present in the Internet Routing Table:   10410
Transit-only ASes present in the Internet Routing Table:406
Average AS path length visible in the Internet Routing Table:   4.3
Max AS path length visible:  55
Max AS path prepend of ASN (265020)  50
Prefixes from unregistered ASNs in the Routing Table:  1071
Number of instances of unregistered ASNs:  1074
Number of 32-bit ASNs allocated by the RIRs:  40454
Number of 32-bit ASNs visible in the Routing Table:   33551
Prefixes from 32-bit ASNs in the Routing Table:  161990
Number of bogon 32-bit ASNs visible in the Routing Table:14
Special use prefixes present in the Routing Table:1
Prefixes being announced from unallocated address space:527
Number of addresses announced to Internet:   3064300672
Equivalent to 182 /8s, 165 /16s and 132 /24s
Percentage of available address space announced:   82.8
Percentage of allocated address space announced:   82.8
Percentage of available address space allocated:  100.0
Percentage of address space in use by end-sites:   99.6
Total number of prefixes smaller than registry allocations:  310145

APNIC Region Analysis Summary
-

Prefixes being announced by APNIC Region ASes:   238444
Total APNIC prefixes after maximum aggregation:   67879
APNIC Deaggregation factor:3.51
Prefixes being announced from the APNIC address blocks:  233482
Unique aggregates announced from the APNIC address blocks:96704
APNIC Region origin ASes present in the Internet Routing Table:   13033
APNIC Prefixes per ASN:   17.91
APNIC Region origin ASes announcing only one prefix:   3749
APNIC Region transit ASes present in the Internet Routing Table:   1754
Average APNIC Region AS path length visible:4.6
Max APNIC Region AS path length visible: 27
Number of APNIC region 32-bit ASNs visible in the Routing Table:   8277
Number of APNIC addresses announced to Internet:  773734912
Equivalent to 46 /8s, 30 /16s and 66 /24s
APNIC AS Blocks4608-4864, 7467-7722, 9216-10239, 17408-18431
(pre-ERX allocations)  23552-24575, 37888-38911, 45056-46079, 55296-56319,
   58368-59391, 63488-64098, 64297-64395, 131072-151865
APNIC Address Blocks 1/8,  14/8,  27/8,  36/8,  39/8,  42/8,  43/8,
49/8,  58/8,  59/8,  60/8,  61/8, 101/8, 103/8,
   106/8, 110/8, 111/8, 112/8, 113/8, 114/8, 115/8,
   116/8, 117/8, 118/8, 119/8, 120/8, 121/8, 122/8,
   123/8, 124/8, 125/8, 126/8, 133/8, 150/8, 153/8,
   163/8, 171/8, 175/8, 180/8, 182/8, 183/8, 202/8,
   203/8, 210/8, 211/8, 218/8, 219/8, 220/8, 221/8,
   222/8, 223/8,

ARIN Region Analysis Summary


Prefixes being announced by ARIN Region ASes:28
Total ARIN prefixes after maximum aggregation:   121596
ARIN Deaggregation factor: 2.19
Prefixes being announced from the ARIN address blocks:   267868
Unique aggregates announced from the ARIN address blocks:128736
ARIN Region origin ASes present in the Internet Routing Table:19057
ARIN Prefixes per ASN: