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2018-05-08

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VPC Glossary

Access Control List

An Access Control List (ACL) can manage (that is, it can allow or deny) ingress and egress traffic for a subnet. An ACL is stateless. Each ACL consists of rules, based upon a source IP, source port, destination IP, destination port, and protocol.

In IBM Cloud VPC, every subnet is created with a default ACL, which allows inbound and outbound traffic, but customers can create custom ACLs. Only one ACL is attached to a subnet at any time, but one ACL can be attached to multiple subnets.

Security Group

A security group acts as a virtual firewall that controls the traffic for one or more servers (VSIs). A security group is a collection of 5-tuple rules that specify whether to allow traffic for an associated VSI. When a customer launches a VSI, he or she can associate one or more security groups with that VSI. Given the correct permissions, customers can modify security group rules.

Public Gateway

A Public Gateway (PGW) enables a subnet (with all the VSIs attached to the subnet) to connect to the internet. Note that subnets are private by default; however, optionally, you can create a PGW and attach a subnet to the PGW. After a subnet is attached to the PGW, all the VSIs in that subnet can connect to the internet.

PGW uses many-to-1 NAT, which means that thousands of VSIs with private addresses will use 1 public IP address to talk to the public internet. PGW does not enable the internet to initiate a connection with those instances. Use the CRUDPGW API to attach and detach subnets to and from your PGW.

Floating IP addresses

Floating IP addresses are public IP addresses that are provided by the system. You cannot bring your own public IP. Floating IP addresses are reachable from the internet, and they can be associated to an instance (for example, a VSI, a loadbalancer, and a VPN gateway). You can reserve a Floating IP address from the pool of available Floating IP addresses provided by IBM, and you can associate or unassociate it to (or from) any instance in the same Virtual Private Cloud.

Region

An IBM Cloud VPC spans multiple regions. Each region contains multiple Zones, which represent independent fault domains. 

Subnet

A subnet is an IP address range, bound to a single Zone, which cannot span multiple Zones or Regions. A subnet can span the entirety of the Zone in the IBM Cloud VPC.

Zone

An independent fault domain. A Zone is an abstraction designed to assist with improved fault tolerance and decreased latency. A Zone guarantees the following properties:

  • Each Zone is an independent fault domain and it is extremely unlikely for two Zones in a region to fail simultaneously
  • Traffic between Zones in a region will be < 2 ms latency

External Links

For more general information, here are some external links you can follow: