REPLY: 2:5005/49 6174fdcc
MSGID: 1:266/420 617581ae
PID: GED+LNX 1.1.5-b20180707
CHRS: UTF8 2
TZUTC: -0400
TID: hpt/lnx 1.9.0-cur 2021-05-15
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: htt
s://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


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