An external phone fails to register with the SIP server after a NAT server is configured on the outbound interfaces of the device functioning as a SIP server

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A SIP server is deployed on an internal network and a NAT server and MTU are configured on the outbound and inbound interfaces of a gateway router on this network. In this case, the router sends fragmented packets to the SIP server and the server returns ICMP Error packets. An external phone fails to register with the SIP server. Disable the MTU configuration on the inbound interface or run the ip soft-forward enhance enable command to enable the enhanced IP forwarding function on the router, so that the external phone can correctly register with the SIP server to implement NAT translation.

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An external phone fails to register with the SIP server after a NAT server is configured on the outbound interfaces of the device functioning as a SIP server
A SIP server is deployed on an internal network and a NAT server and MTU are configured on the outbound and inbound interfaces of a gateway router on this network. In this case, the router sends fragmented packets to the SIP server and the server returns ICMP Error packets. An external phone fails to register with the SIP server. Disable the MTU configuration on the inbound interface or run the ip soft-forward enhance enable command to enable the enhanced IP forwarding function on the router, so that the external phone can correctly register with the SIP server to implement NAT translation.

SIP users fail to be registered after outbound NAT is configured and canceled on the public network interface of the AR
Q: SIP users fail to be registered after outbound NAT is configured and canceled on the public network interface of the AR. A: SIP users connect to the SIP server through the AR enabled with outbound NAT. The ALG function is disabled for SIP, so STP packets cannot traverse the NAT device. As a result, the SIP server cannot communicate with SIP users and SIP users fail to be registered. When registration request packets of SIP users pass through the AR, the AR generates NAT session entries to record packet information and updates entries and the aging time after new packets are received. After the aging time is reached, the NAT session entries that fail to be updated are automatically cleared. Therefore, the SIP users that fail to be registered continue to send registration request packets. NAT session entries cannot be directly cleared after outbound NAT is canceled, and are automatically cleared after the aging time is reached. Because SIP users continuously send registration request packets, the AR continuously update NAT session entries and theaging time. That is, the NAT session entries cannot be automatically cleared. As a result, the SIP users fail to be registered. Run the nat alg command to enable ALG for SIP so that the SIP server can communicate with SIP users after outbound NAT is configured. In addition, run the reset nat session all command to forcibly clear the NAT session entries and quickly change the NAT configuration. Or, you can run the reset nat session all command to forcibly clear NAT session entries after outbound NAT is canceled, so that the SIP server can communicate with SIP users. Note: Deleting NAT mapping entries may affect exchange of some packets.

How to configure dual uplink interfaces on an AR functioning as the NAT server
A Huawei AR router functioning as a NAT server supports dual outbound interfaces. For the network diagram, see the right side of the page. The web server uses internal IP address 192.168.0.100/24 and port 8080 to provide services. The IP address of GE2/0/0 (outbound interface) on the AR is 202.10.1.2/24, and the IP address of GE3/0/0 is 201.10.1.2/24. The configuration process is as follows: 1. Configure IP addresses of interfaces on the router. [Huawei] interface Ethernet0/0/0 [Huawei-Ethernet0/0/0] ip address 192.168.0.1 24 [Huawei-Ethernet0/0/0] quit [Huawei] interface GigabitEthernet2/0/0 [Huawei-GigabitEthernet2/0/0] ip address 202.10.1.2 24 [Huawei-GigabitEthernet2/0/0] quit [Huawei] interface GigabitEthernet3/0/0 [Huawei-GigabitEthernet3/0/0] ip address 201.10.1.2 24 [Huawei-GigabitEthernet3/0/0] quit 2. Configure outbound NAT on GE2/0/0 and GE3/0/0 in NAT server and Easy IP mode. [Huawei] acl number 2000 [Huawei-acl-basic-2000] rule 5 permit source 192.168.0.0 0.0.0.255 [Huawei-acl-basic-2000] quit [Huawei] interface GigabitEthernet2/0/0 [Huawei-GigabitEthernet2/0/0] nat server protocol tcp global 202.10.1.3 www inside 192.168.0.100 8080 [Huawei-GigabitEthernet2/0/0] quit [Huawei] interface GigabitEthernet3/0/0 [Huawei-GigabitEthernet3/0/0] nat server protocol tcp global 201.10.1.3 www inside 192.168.0.100 8080 [Huawei-GigabitEthernet3/0/0] nat outbound 2000 [Huawei-GigabitEthernet3/0/0] quit

Can outbound NAT and NAT server be configured simultaneously on an AR
On an AR router, outbound NAT and NAT server can be configured simultaneously on an interface. For detailed configurations, see "Internet Access > NAT > Example for Configuring NAT to Enable Users to Access the Internet and Provide the WWW Service Externally" in the Typical Configuration Examples.

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