Hi I m trying to use awsx to create a VPC with 9 subnets I w

Question

Hi I m trying to use awsx to create a VPC with 9 subnets I want 2 sets of 3 smaller subnets and one set of 3 large subnets My VPC uses a ` 16` mask I m trying to use a ` 18` mask for my 3 large subnets and a ` 21` mask for my 6 smaller subnets But VPC creation fails because it cannot come up with non overlapping subnets Am I missing something or is this maybe a gap in the awsx VPC computation the ` 18` mask gives me 4 prefixes that I can assign to the 3 subnets leaving one prefix I can give to the 6 smaller subnets ` 21` should give me 8 subnets using the remaining prefix

billowy-army-68599 · Answer

It s a gap in the computation You ll have to define your own cidrs

brief-church-51632 · Answer

is there some way to do that using awsx Or I d have to use the raw aws interfaces

billowy-army-68599 · Answer

I m not on my laptop but there s an option to define subnets and their mask

billowy-army-68599 · Answer

Inside awsx

salmon-account-74572 · Answer

The details for specifying subnets with AWSX VPC can be found here <https www pulumi com registry packages awsx api docs ec2 vpc subnetspec>

salmon-account-74572 · Answer

OK if I m following your desired subnet design correctly you d end up with four 18 prefixes ```10 0 0 0 18 10 0 64 0 18 10 0 128 0 18 10 0 192 0 18``` And then you d like to take one of these four prefixes I ll use the last one and subdivide it into eight smaller subnets ```10 0 192 0 21 10 0 200 0 21 10 0 208 0 21 omitting for brevity 10 0 248 0 21``` Is that right

salmon-account-74572 · Answer

< brief church 51632> I ve been having some conversations with our engineering team and assuming I am understanding what you re trying to do we are reasonably certain that AWSX can t be configured to do what you re trying to do You can however use the AWS provider and construct the VPC subnets routes route tables Internet and NAT gateways etc according to the plan you re describing Let me know if you want some help building this out

brief-church-51632 · Answer

The snippet above is exactly right Thanks a bunch for following up I think I can live with the limitations of the current implementation for now though it would be nice to get some more control over this from awsx I did start down the road of setting it all up on my own and it s quite onerous awsx takes care of a lot of boilerplate for you

brief-church-51632 · Answer

like maybe just a wrapper around Subnet which lets you set the CIDR but takes care of creating a ngw if requested creates the route table and sets up the routes to the ngw igw would be nice

salmon-account-74572 · Answer

< brief church 51632> That s a neat idea Maybe I ll play around with something like that if I can find some extra time smile One of our engineers does have an in flight PR that allows some additional flexibility around subnets and CIDRs with the AWSX VPC Their implementation would come in the form of reservations each of which defines the CIDR for a particular subnet The subnet creation engine would then consume these reservations when it creates the subnets or calculate the CIDR if no reservation is present I think that would enable you to do what you re seeking although it would require you to define all the subnet CIDRs as reservations so a bit of a trade off