OK, my company just purchased a WISP. They have a completely Layer2, bridged network from the core switch to the subscribers, there is routing between the intertie and their internal network, so I guess I can’t say it was COMPLETELY bridged..
As you can imagine there is an extreme amount of broadcast packets traversing the internal network. I want to fix this by breaking up the collision domains so they’re isolated per AP.
I also want to use private side addressing for all my equipment, PtP links, PtMP AP’s, etc. However I want to give my subs publically routeable IP addresses. My ISP gave me a /22 subnet so I have 1022 unsubnetted IPs to play with. Which is not very many seeing as our business plan calls for an additional 500 subs by years end (however we’re shooting for double that). I’ve also been told when I need more IP’s I’d be given a whole new network (I have the end of whatever part of a class B they have).
Is it possible to do this, I’m thinking given the limited IP’s I have, I may have to do private addressing for subs and just hand out public IP’s on a request only basis…
You must devide your /22 public subnet into smaller ones
/23 - 510 users per subnet
/24 - 254 users per subnet
/25 - 126 users per subnet
/26 - 62 users per subnet
/27 - 30 user per subnet
/28 - 14 users per subnet
You can create any mix of this subnets. If you have
3 AP with less than 62 users
4 wired networks with less than 126 users
1 wired network with less than 254 users
2 Ap with less than 30 users
you need to devide your /22 into 1 x /24, 4 x /25, 3 x /26, 2 x /27
If you don’t have enough IP addresses it will be necessary to hide them behind the NAT - leave one small subnet for the NAT purpuses
I understand subnetting.. my delima is I have ~30 AP’s that I’d like to have support for 50 users per AP for future expansion.. so I’d need a 26bit subnet for each AP.. with a 22bit subnet to work with it makes it impossible to do it with the public IP’s. So I guess I just answered my question, I have to NAT.
Since you expect to use up a /22 within a year, you should just apply to Arin. As long as you have a minimum of two upstream providers, a /22 is acceptable.
If you can justify a /20 to Arin, then you don’t even need to be multi-homed.
Having your own PA space is much nicer than using a chunk out of some other ISPs space. This way, you can drop providers without renumbering.
Also, I wouln’t pre-allocate a large amount of space per AP, just add more space as needed. Or, in this size network, you could use OSPF to advertise /32s, thus keeping everything portable (and efficient).
Yes, this is a very important thing. I survived 2 complete changing of public IP addresses on my network, and I can tell that it was REALLY very painfull. Over a week after changing the addresses, there was some hidden places where the old ones have been forgotten… a real nightmare
Oh yeah, I know all the pains of switching address spaces. Already had to do that once, don’t want to take that one on again! Thanks for the suggestions, I’m looking into applying for an address space from ARIN as we speak.
We just got a /21 for our network and it was like pulling teeth. You can get < /23 easily but anything more they really want your left arm for it. There are 2 types of blocks, end user and ISP. If you provide space to end users you have to get the ISP block and it costs you each year to renew it. If you need help along the way let me know.
PS - if you have your own ip space be prepared to run bgp or have your provider annouce them for you.
Yeah well going over the requirements for ARIN at present I’m only using a 57% of a /22 bit subnet.. So qualifying for a /21 or /20 might be difficult. I’m going to send in an app anyway to see what they come back with. Cause I’d rather get an address space we can stick with for awhile without having to resubnet and renumber the network.
Definitely worth almost every work
We have a /20 PI address space and that’s REALLY nice. We did a re-numbering for a /22 two times before (that’s several years ago, thanks god). That was really no fun at all.
If you are in the position to get enough own address space right now, DO IT. It’ll save you more than one headache in the long run…
