Difference between NACLs and SGs
NACL and SG are both firewall rules, however they have notable differences that I have summarized in the following table:
NACLSG Scopes subnet or VPC - applies to all instances in the subnet or VPC instance - applies to all instances linked to the SG Cardinality 1 NACL per subnet or VPC 1 to many SG per instance or instance group Actions allow or deny allow - every unspecified rule defaults to deny States stateless - i.e. NACLs allow traffic looking at the IP and port regardless of the fact that it is a reply request statefull - i.e. SGs automatically allow a reply to be returned. They maintain a state table that tracks the origin and destination IP and port. Only one rule (inbound or outbound) is required Rule order rules are applied in order rules are applied simultaneously
Note that inbound traffic first passes through the NACL firewalls then to the SG firewalls. Outbound traffic goes the opposite way.
Firewall requirement for EKS
The AWS documentation specifies the following requirements:
- traffic needs to be allowed between the control plane and managed node groups
- traffic needs to be allowed between nodes
- nodes and control plane should have outbound access to the internet.
Note that one of the possibilities your nodes might not join your cluster is if they do not have access to the internet. Indeed, they need access to the Amazon EKS API.
SG configuration for EKS
Taking into account above consideration, here is an SG proposition for EKS.
Inbound
ProtocolPortSource TCP 443 self TCP 1024 - 65535 self
Outbound
ProtocolPortDestination TCP 443 0.0.0.0/0 TCP 80 0.0.0.0/0 TCP 1024 - 65535 0.0.0.0/0
NACL configuration for EKS
Taking into account above consideration, here is a NACL proposition for EKS.
Inbound
Rule #ProtocolPortSourceAllow / Deny 100 TCP All self Allow 200 TCP 1024 - 65535 0.0.0.0/0 Allow 9000 All All All Deny
Outbound
Rule #ProtocolPortDestinationAllow / Deny 100 TCP All self Allow 200 TCP 1024 - 65535 0.0.0.0/0 Allow 300 TCP 80 0.0.0.0/0 Allow 400 TCP 443 0.0.0.0/0 Allow 9000 All All All Deny
I hope this article will help you set up your EKS security group (SG) and network access control list (NACL) firewalls easily. If you have other recommendations, questions or challenges please reach me in the comment section. Take care.
