Ports Used for IPSec (2024)

FAQs

Ports Used for IPSec? ›

IPSec VPN. IPSec VPN is a layer 3 protocol that communicates over IP protocol 50, Encapsulating Security Payload (ESP). It might also require UDP port 500 for Internet Key Exchange (IKE) to manage encryption keys, and UDP port 4500 for IPSec NAT-Traversal (NAT-T).

IKEv2 uses non-standard UDP ports so you need to ensure that these ports are not blocked on the user's firewall. The ports in use are UDP 500 and 4500.

Port 4500, often paired with the UDP protocol, is fundamental in the deployment of IPsec VPNs, serving as a conduit for secure communications across internet protocols.

For IPsec to work with NAT traversal, these protocols must be allowed through the NAT interface(s): IKE - UDP port 500. IPsec NAT-T - UDP port 4500.

By default, L2TP uses IPSec, which requires UDP ports 500 and 4500, and ESP IP Protocol 50. If you disable IPSec, Mobile VPN with L2TP requires only UDP port 1701.

As IKEv2 uses UDP, it has relatively low latency and will be a speedy option for most use cases. It also isn't very demanding for performance, so works well on weaker hardware devices.

Transmission: Encrypted IPsec packets travel across one or more networks to their destination using a transport protocol. At this stage, IPsec traffic differs from regular IP traffic in that it most often uses UDP as its transport protocol, rather than TCP.

IPSec VPN. IPSec VPN is a layer 3 protocol that communicates over IP protocol 50, Encapsulating Security Payload (ESP). It might also require UDP port 500 for Internet Key Exchange (IKE) to manage encryption keys, and UDP port 4500 for IPSec NAT-Traversal (NAT-T).

IKEv2/IPSec's ability to connect quickly makes it great for mobile phones using cellular data. L2TP/IPSec is best for manual VPN configuration since it's easy to set up.

What ports does Cisco AnyConnect use for IPSec? ›

Traffic on UDP port 500 is used for the start of all IKE negotiations between VPN peers. This is true of all IPSec platforms. In some cases, UDP port 4500 is also used.

IPSecVPN: From the Port Forwarding screen, set Local Port to 500 and Protocol to UDP for IPSecVPN tunnel, and then set Local Port to 4500 and Protocol to UDP for IPSec tunnel.

In computing, IKEv2 is a VPN tunneling protocol ensuring safe online communication between two devices. IKEv2 works with the IPsec protocol, forming a VPN protocol called IKEv2/IPSec. IKEv2 helps devices recognize each other, and the IPsec protocol provides security when transporting data.

IKEv2 VPN: A standards-based IPsec VPN solution that uses outbound UDP ports 500 and 4500, along with IP protocol number 50.

The IKE protocol uses UDP packets, usually on port 500, and generally requires 4–6 packets with 2–3 round trips to create an ISAKMP security association (SA) on both sides. The negotiated key material is then given to the IPsec stack.

This informs the client and server involved that the TLS protocol will be used in the data transfer. Browsers can make a direct request, or they can just open a port used by TLS. This is generally port 443.