![]() Stopping IKE and AuthIP IPsec Keying Modules. AssumeUDPEncapsulationContextOnSendRule in the Windows registry. I've studied and tried adjustments in these areas: IP protocol stack, at a level above WinPcap, that drops the packets because they don't belong to any VPN association local to the server. I want Windows to be agnostic to that traffic, and let a raw socket capture and process it. Other UDP ports are captured without problems, but UDP port 4500 is different. Remember that WinPcap is a Windows driver, so if it captures that traffic is because it traverses the IP protocol stack.īut I am unable to capture it with a. WinPcap and the accompanying Wireshark tool (running on the same server) capture the missing traffic. I know few people use Windows in this kind of role, but IĬan't understand why this is impossible to accomplish. Windows 2008 drops every packet destined to UDP port 4500, preventing it from acting as a general purpose IP/IPSec gateway (a machine that routes IP/IPSec traffic on behalf of external computers). I don't want to be rude, but this is definitely not a valid answer to my question. We don't know if this URL can help ( ) or else shutting down any of these services (IKE and AuthIP IPsec Keying Modules, IPsec Policy Agent). The question is: how can we prevent Windows from interacting with IPSec NAT-T packets received on UDP port 4500, so that they are received by a RAW socket bound to the appropriate network interface? If we send something to UDP port 4500, the packet is not received by the RAW socket, no matter whether or not the IP address is owned by the network interface. If we send an arbitrary UDP packet to a UDP port other than 4500, the packet is received by the RAW socket. The program just receives IP packets with a RAW socket. We have created a test program to comfirm the problem is there. Cisco must be aware of the problem, and must have decided to change the ports chosen by their client for Windows. The case that doesn't work uses NAT-T with UDP port 4500 on both sides. The case that works uses NAT-T using a random UDP port from the external computer and UDP port 4500 on the VPN termination side. We have compared those same packets produced by the Cisco VPN client in an external Windows computer and the result is that there is a difference in the UDP ports used: We have isolated the problem: certain NAT-T packets arrive at the server (Wireshark tells us so), but the RAW socket doesn't receive them. The inbound packet is discarded when IP tries to find an associated tunnel definition because there are no tunnels defined. Interestingly, Cisco VPN client in Windows works. Error description Inbound UDP port 4500 is treated as UDP encap ESP packets used for NAT-T when IPSECURITY is coded for IPCONFIG. ![]() We have problems with one type of traffic: NAT-T generated by a Cisco VPN client in Mac, Android VPN client. The Windows server actsĪs a gateway for that traffic for those external computers.įor downlink traffic, it receives it in the RAW socket, determine the tunnel id from the destination address, and tunnels the traffic back to the destination. That way, the traffic can even be for IP addresses other than the server's own addresses. It receives IP traffic from external computers tunneled in GTP (a tunneling protocol), deencapsulates it and forwards it through a RAW socket. 500/UDP: IPSec Phase 1 prior to NAT detection (after NAT detection, 4500/UDP is used).We have a Windows 2008 server with a service installed that acts as an IP tunnel gateway. 4500/UDP: IPSec NAT Traversal (for all signaling, data, voice traffic). 443/TCP: Https over TLS/SSL for provisioning and management traffic. Note: All ports listed need to be configured for inbound and outbound connections. Please see the manufacturer's documentation. Ensure the modem / router is using the latest software (firmware). If the MicroCell is connected to a router that is connected to a modem and both the router and the modem have NAT (Network Address Translation) enabled, disable NAT either in the router or the modem. If using multiple routers, the Microcell must be connected to the first router connected to the broadband modem MAC address filtering is either turned off or allowing the MAC address of the AT&T MicroCell IPSec Pass-Through is Enabled Data is not restricted from passing through ports 4500 and 500 (AKA Port Blocking). Please be advised that the router manufacture or the ISP provider will not provide support for AT&T MicroCell, but they can assist with configuring the following router settings: Had to log into my router and set MTU size to 1492 and then set Block Fragmented Packets to Disabled. My default router settings (MG-7540) were stopping the network connect. He sent me a link to setting up my router that is not in the User manual. Took numerous calls to ATT until reaching a bright young man.
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