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VPC Firewall Rules Overview

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VPC Firewall Rules allow developers to granularly control access to VPC networks, subnets, and individual VMs.

Concepts​

VPC Firewall Rules rely on a five-tuple to filter L3 traffic and determine if it is allowed to pass:

  • Action: what action to take for categories of traffic, allow or deny
  • Direction: what direction traffic is heading, relative to the VM, ingress is "outside world to the VM" and egress is "VM to the outside world"
  • Protocols: what protocols are filtered, tcp, udp, or icmp
  • Source: the IP (or IPs) and port (or ports) that traffic is "coming from" (the "outside world" in an ingress rule; the VM in an egress rule)
  • Destination: the IP (or IPs) and port (or ports) that traffic is "heading to" (the VM in an ingress rule or the "outside world" in an egress rule;)

By default, all traffic is denied unless a rule explicitly allows it.

Default Firewall Rules​

Crusoe provides the following default firewall rules in the default VPC network.

Ingress:

  • default-allow-ssh: allow SSH access from the public internet to all instances
  • default-allow-icmp-internal: allow ICMP traffic from all VMs on the same network; note this does not allow public ICMP traffic
  • default-allow-internal-network: allow all TCP and UDP traffic from all VMs on the same network

Egress:

  • default-allow-icmp-egress: allow all ICMP traffic from all VMs on the network to egress to the public internet
  • default-allow-tcp-udp-egress: allow all TCP and UDP traffic from all VMs on the network to egress to the public internet

If you do not want to allow this traffic, you can delete one or all of these rules.

Firewall Rules in non-default VPCs​

Non-default (custom) VPC networks are not created with any default firewall rules. Firewall rules implicitly deny traffic unless a rule explicitly allows the traffic to pass, so all communication to/from non-default VPC network will be denied until firewall rules are added to allow desired traffic.

In order to allow ingress and egress communication for non-default VPC, explicit firewall rules have to be configured for ingress/egress. We recommend starting with the default firewall rules above, and modifying them as desired.

Tips for using Firewall Rules​

A few tips for using Firewall Rules:

  • Source ports may not be the same as the destination ports (e.g. SSH may not come from port 22, but it will arrive at port 22)
  • Destination IPs always reference the private IP (172.27.x.x) as opposed to the public IP

Limitations​

Mixing protocols​

At the current time, you can only create tcp and/or udp, or icmp rules. You cannot create a mix of tcp or udp with icmp. Similarly, you cannot add ports to an icmp rule.

Allow only/implicit deny​

At the current time, firewall rules only support allow rules. By default, all traffic is denied unless it is specifically allowed. We do not currently have plans to support deny rules.

Port restrictions​

For security reasons, Crusoe does not allow SMTP traffic on ports 25 or 587.