Subj : A small questionary on ISPs
To   : Victor Sudakov
From : Scott Street
Date : Sun Oct 24 2021 11:23:02

Hello Victor!

24 Oct 21 13:26, you wrote to me:


 SS>>>>     inet6 2601:48:c500:9340::c0e3 prefixlen 60 dynamic
 VS>>> This is very interesting. Why "prefixlen 60" on the LAN?

 VS> Whatever Comcast's intentions, are you sure that a LAN with a
 VS> prefixlen different from /64 will work properly? Will a non-standard
 VS> prefix not break SLAAC and other things?

 VS> This is where my theoretical knowledge is lacking, but I've always
 VS> been warned against using anything different from /64 on a LAN
 VS> segment.

The gateway and my dozen+ devices do not seem to have any issues getting dynamic IPv6 addresses, and since most are Apple, IPv6 is the prefered connection method.  As an "end-user", I don't know why Comcast has chosen to give my network MORE address space; like 1800000000000000000+ addresses wasn't enough; they've given me 295000000000000000000+ addresses.

In reality, for an end user network, /96 is plenty with 2^32 addreses, and /112 is even more reasonable with 2^16 addresses;  especially when you compare it to the default settings on every consumer IPv4 gateway with 2^8 addresses.

I found this nice table from IBM on IP address subnet masks: https://www.ibm.com/docs/en/ts3500-tape-library?topic=formats-subnet-masks-ipv4-prefixes-ipv6
(its odd that they buried it in a tape library document, but almighty Google found it! - Google KNOWS EVERYTHING!)  :)


Cheers,

Scott


---
 * Origin: -={ The Digital Post }=- (1:266/420)

.