Whether L2TP registration port 1701 can be modified on the USG2000 or USG5000

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The L2TP communication port 1701 cannot be modified on the USG2000 or USG5000.

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Pass-through ports configured for L2TP over IPSec on the USG2000 and USG5000
The pass-through ports configured for L2TP over IPSec on the USG2000 and USG5000 are as follows: 1. Port 500 is initially used for IKE negotiation. After the NAT-T capability detection and NAT gateway detection are complete, the number of the UDP port that encapsulate ISAKMP messages is changed to 4500. This port is used for subsequent negotiations and data transmission. 2. L2TP is registered with UDP port 1701. However, this port is only used for initial tunnel establishment. The L2TP tunnel initiator (LAC) selects any idle port (may not necessarily be port 1701) to send packets to port 1701 on the receiver end; upon receiving the packets, the LNS also selects any idle port (may not necessarily be port 1701) to send packets to the specified port of the LAC. Therefore, ports of both ends are specified and remain unchanged within the tunnel connection period. 3. According to the L2TP over IPSec mechanism, packets are encapsulated based on L2TP and then IPSec. Therefore, port 1701 that transmits L2TP packets is used as a matching condition. All encapsulated L2TP packets are transmitted over the IPSec tunnel. Therefore, if the L2TP over IPSec is configured but no NAT traversal is available, port 500 and port 1701 are configured as pass-through ports. If the NAT traversal is available, port 500, port 4500, and port 1701 are configured as pass-through ports.

Whether the L2TP domain name and tunnel key are case-sensitive on the USG2000 and USG5000
On the USG2000 and USG5000, the L2TP domain name is case-insensitive but the tunnel key is case-sensitive.

Difference between the L2TP and the IPSec on the USG2000 and USG5000
The L2TP provides tunnel transmission support to data frames on the PPP link layer and allows L2 link terminations and PPP session points reside on different devices, thereby expanding the PPP model. That is, the L2TP establish a PPP link between a cross-LAC user and the LNS. The IPSec is an open network-layer security framework protocol, stipulated by the Internet Engineering Task Force (IETF). It is a series of protocols and services that provide IP network security. The IPSec mainly includes the Authentication Header (AH), Encapsulating Security Payload (ESP), Internet Key Exchange (IKE), and algorithms used for network authentication and encryption. The L2TP over IPSec mechanism encapsulates packets based on the L2TP and then the IPSec. In this way, the L2TP over IPSec mechanism integrates advantages of two types of VPNs, implements user authentication and address allocation based on the L2TP, and makes up the disadvantages of the IPSec in terms of user authentication and authorization.

Method used to configure L2TP parameters on the USG2000 and USG5000
The method used to configure L2TP parameters on the USG2000 and USG5000 is as follows: 1. allow l2tp The allow l2tp command is used to specify the name of the peer tunnel that accepts the call and the used Virtual-Template. allow l2tp virtual-template virtual-template-number [ remote remote-name ] [ domain domain-name ] [ vpn-instance vpn-instance-name ] 2. call-lns local-user The call-lns local-user command is used to perform L2TP dialup on the LAC to access the LNS, so as to establish an L2TP tunnel. call-lns local-user username 3. l2tp domain suffix-separator The l2tp domain suffix-separator command is used to set the suffix separator. l2tp domain suffix-separator separator 4. l2tp match-order The l2tp match-order name is used to set the sequence of the called number and domain name used to search for the L2TP group. l2tp match-order { dnis | dnis-domain | domain | domain-dnis} 5. l2tp sendaccm enable The l2tp sendaccm enable command is used to enable the function of sending ACCM messages by the L2TP. By default, the function of sending ACCM messages by the L2TP is enabled. l2tp sendaccm enable 6. l2tp-group The l2tp-group command is used to create an L2TP group. l2tp-group group-number 7. l2tpmoreexam enable The l2tpmoreexam enable command is used to enable the LNS to accept L2TP connection requests initiated by different L2TP instances using the same tunnel name. l2tpmoreexam enable 8. l2tp up-down log enable The l2tp up-down log enable command is used to enable the function of sending logs upon L2TP user getting online or offline. l2tp up-down log enable 9. mandatory-chap The mandatory-chap command is used to forcibly perform the CHAP verification again between the LNS and the client. By default, the system does not re-verify the CHAP. mandatory-chap 10. mandatory-lcp The mandatory-lcp command is used to re-negotiate the Link Control Protocol (LCP) between the LNS and the client. By default, the system does not re-negotiate the LCP. mandatory-lcp 11. start l2tp The start l2tp command is used to specify the trigger conditions for originating calls when the local end serves as the L2TP LAC. start l2tp { lns-domain domain-name | ip ip-address &<1-5> } { domain domain-name |fullusername user-name } [ vpn-instance vpn-instance-name ] 12. tunnel authentication The tunnel authentication command is used to enable the L2TP tunnel verification. tunnel authentication 13. tunnel avp-hidden The tunnel avp-hidden command is used to configure the transmission mode in which the Attribute Value Pair (AVP) data is hidden. tunnel avp-hidden 14. tunnel name The tunnel name command is used to specify the local tunnel name. tunnel name tunnel-name 15. tunnel password The tunnel password command is used to specify the password used for tunnel verification. tunnel password cipher password 16. tunnel source The tunnel source command is used to configure the source tunnel interface used by the LAC to initiate a tunnel establishment request to the LNS. tunnel source loopback interface-number 17. tunnel timer hello The tunnel timer hello command is used to set the interval for sending Hello packets over the tunnel. tunnel timer hello interval 18. virtual-l2tpforward enable When the IP address used by the LNS to access the intranet and the IP address allocated by the LNS to the client are in the same network segment, you can use the virtual-l2tpforward enable and arp-proxy enable command together to enable the L2TP virtual forwarding function. virtual-l2tpforward enable

Method used to configure the L2TP over IPSec user address segment on the USG2000 and USG5000
The method used to configure the L2TP over IPSec user address segment on the USG2000 and USG5000 is as follows: Configure the L2TP over IPSec user address segment using the CLI: # Define an address pool and allocate an IP address to the dial-up user. [LNS] aaa [LNS-aaa] ip pool 1 10.1.1.1 10.1.1.100 # Set the user name and password (consistent with those configured on the PC of the employee on a business trip). [LNS-aaa] local-user vpdnuser password cipher Hello123 [LNS-aaa] quit # Allocate an address in the IP address pool to the peer interface. [LNS] interface virtual-template 1 [LNS-Virtual-Template1] remote address pool 1 [LNS-Virtual-Template1] quit Configure the L2TP over IPSec user address segment using the web UI: Configure the L2TP parameters. 1. Choose Network > L2TP > L2TP. 2. In Configure L2TP, select Enable and click Apply. 3. In L2TP Group List, click New. 4. Set Group Type to LNS. 5. Configure the L2TP parameters. The server address shall be in the same network segment as the address in the address pool. In this way, you do not need to configure a route. Peer Tunnel Name must be consistent with Local Tunnel Name configured on the LAC. Group Type: LNS Peer Tunnel Name: LAC Tunnel Password Authentication: Enable Password Type: Ciphertext Tunnel password: Hello123 Confirm Tunnel password: Hello123 User Group: default Set the user address allocation parameters as follows: Server Address/Subnet Mask: 10.2.1.1/255.255.255.0 User Address Pool: 10.2.1.2-10.2.1.100 6. Click OK.

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