Provide Support for the Cisco VPN Client In most cases, IPSec VPN traffic does not pass through ISA Server 2000. However, Cisco Concentrator 3300, with the latest firmware updates, uses "transparent tunneling" that uses User Datagram Protocol (UDP) ports 500, 4500, and 10000 to communicate securely between VPN clients and concentrators.
IPsec is faster than OpenVPN, so if both client and server support IPsec, use IPsec. Use External Authentication ¶ For user-based authentication, the most efficient method of user management for large numbers of accounts is an external authentication source, such as a RADIUS server, LDAP server, Active Directory (Via LDAP or RADIUS/NPS), etc. How to build a remote user access VPN with Racoon In this VPN solution, the client needs to send UDP packets to ports 500 and 4500 of the VPN gateway. The first packets are exchanged on port 500, then NAT-T negotiation moves the transaction to port 4500. Firewalls in front of the VPN gateway must be configured to let udp/500 and udp/4500 pass through to the VPN gateway. VPN gateway and RADIUS Configuring NAT Transparent Mode for IPSec on the VPN 3000 Jan 14, 2008
SonicWall IKE VPN negotiations, UDP Ports and NAT
VPN Protocols - IPVanish IKEv2 (Internet Key Exchange Protocol Version 2) IKEv2, a protocol made available exclusively …
IPsec is faster than OpenVPN, so if both client and server support IPsec, use IPsec. Use External Authentication ¶ For user-based authentication, the most efficient method of user management for large numbers of accounts is an external authentication source, such as a RADIUS server, LDAP server, Active Directory (Via LDAP or RADIUS/NPS), etc.
OpenBSD FAQ: Virtual Private Networks (VPN) To enable the initiator to reach the responder, the isakmp UDP port should be open on the responder. If one of the peers is behind NAT, the ipsec-nat-t UDP port should also be open on the responder. If both peers have public IPs, then the ESP protocol should be allowed. EdgeRouter - Modifying the Default IPsec Site-to-Site VPN UBNT_VPN_IPSEC_FW_HOOK Allow UDP port 500 (IKE), UDP port 4500 (NAT-T) and ESP in the local direction. UBNT_VPN_IPSEC_FW_IN_HOOK Allow IPsec traffic from the remote subnet to the local subnet in the local and inbound direction. UBNT_VPN_IPSEC_SNAT_HOOK Exclude all traffic from the local subnet to the remote subnet from NAT. Testing Sophos SSL VPN Performance - UDP or TCP? Countries or regions that may block VPNs typically block IPSEC tunnels but not TCP SSL VPNs because it would break HTTPS and therefore most of the Internet. SSL VPN over UDP still attempts to connect to the VPN server on port 443, but unlike HTTPS traffic that uses TCP as a transport protocol, it uses UDP. Some firewalls and proxies may flag How to Configure the Android VPN Client for IPsec Shared