AWS ... VPCs, IP addresses, Lambdas, Network Interfaces and Security Groups

2021-10-26 networks / aws

So this is just a tiny note to mention that if you’ve got an AWS VPC subnet, and it seems to be running out of address space even though it’s got nothing much in it but a bunch of Lambda functions, you can find out what’s using the addresses by going to …

This will actually give you a list of all the things using IP addresses in your subnet(s). Lambdas use an IP address per subnet per security group, because security groups are a IP-level construct like a firewall routing table.

So if each lambda has its own SG then it’ll also have it’s own IP, even if all the SGs rules are the same, just in case they change.

So either get yourself some bigger subnets, or share that SG between lambdas.