[kotaKat]

there's a couple subnets I (ab)use in the DOD IP space for my home network knowing they'd never put them on the open internet. it's also fun to throw logging for a loop if someone digs.

22.0.0.0/8 - it's basically free real estate!

[walrus01]

the entirety of 10/8 and 172.16/12 and 192.168/16 wasn't large enough for your house?

[xoa]

>the entirety of 10/8 and 172.16/12 and 192.168/16 wasn't large enough for your house?

Just to chime in agreeing with sibling comments, the issue is when it's not about just your house and you're deep into self-hosted stuff with a lot of different properties and businesses other people's houses all sharing resources. Without a lot of coordination and consideration, which in practice doesn't really happen easily given the adhoc nature such things tend to organically develop out of, and all the random stuff that wants specific addresses at least for setup, it actually gets pretty easy to run into collisions. Allocations typically are definitely inefficient in many respects but also made sense in the context they were first done and of course can be a certain amount of effort to change.

In an ideal world I sorta feel like "IPv6" should have been more along the lines of <12 octet prefix>:<IPv4>, everyone gets a prefix or set of prefixes that they actually own and are consistent worldwide, or at least only change when geographic location changes, and then can just have the entire 32-bit IPv4 space for LAN however they want. Then you only have to care about prefix between LANs and it could all be extremely automated, internally you only need to use something that looks like IPv4 with the network hardware transparently able to handle prefixes for WAN. Backwards compatibility story would be a lot more straight forward too. Oh well.

@kotaKat: that's a great idea and I don't know why I forgot I played with that like 15 years ago. Really handy as a backup space that almost certainly won't collide with any commercial hardware at least.

[ErroneousBosh]

I work for a large organisation that has various blocks scattered around 10./8, some with highish values for the second octet and some with lowish values, so say 10.129.0.x/24 and 10.3.0.x/24 to pick just two out of a couple of thousand.

But one of our vendor networks uses 10.32.x.x/32 for various radio gateways, and the radios themselves all locally expose (this is where I give away too big a clue as to what I do) 10.0.0.101 as a management address that emits important link status data.

So you can imagine what a godawful bùrach everyone's routing tables are.

[kotaKat]

i deal with a lot of nerds that are all interconnected with one another and nobody can agree on a common subnet for their houses when we all decide to exchange routes internally. ;)

[myself248]

I deal with a lot of nerds, but starting in about 2008 we all segmented up the 10.x space and each of us has a /16, with each site we manage having typically a /24 or /22, so nobody overlaps. We can light up tunnels between each other and never have a collision. We have a little internal registry on a private wiki, and it's been serving us well for... oh dear, almost two decades now.

Crucially, we set aside the common 10.1 and 10.10 ranges as nonroutable, so any devices that default into those have to be dealt with before they can live on the wider network.

Newcomers get handed a block and have to renumber, or NAT into it, or whatever, but they cannot emit bogons. At a small scale (first-name basis), this works.

[cryptonym]

I have seen ISP doing CGNAT on DOD IP space.

[bityard]

The CGNAT space (100.64.0.0/10) is also free real estate for container virtual/overlay networks when you don't want to (or can't, thanks to IT) use the RFC-1918 subnets.

[webstrand]

I also do this, except 7.0.0.0/8 instead. Its great for not conflicting with hotel wifi dhcp.