When an AR router is used as the PPPoE client, the Internet access rate of the LAN users connected to the device is low


In the dialer interface view, run the tcp adjust -mss value command to set the maximum TCP segment size of the interface.

In scenarios of PPPoE application, it is recommended that the value used in the tcp adjust -mss command should be 1200.

The maximum transmission unit (MTU) of the PPPoE interface is 1492 bytes. If the packets which are forwarded in Layer 2 and transmitted upward through the interface are larger than the MTU size and cannot be fragmented as configured, the packets cannot be sent, which results in the low Internet access rate of users. In this case, you can run the tcp adjust -mss command in the dialer interface view to modify the maximum segment size (MSS) value determined in the TCP negotiation phase, ensuring that the packet size is smaller than the MTU size of the dialer interface so that the packets can be processed properly and improving the Internet access rate.

Other related questions:
AR router troubleshooting guide: An AR router cannot access the Internet through PPPoE dial-up connections
For the problem that an AR router cannot access the Internet through PPPoE dial-up connections, see the troubleshooting guide. For details, access the URL in the right column.

Configure an internal user to access the network using Easy IP on the AR router
A Huawei AR router allows internal users to access external servers using Easy IP. The IP address of GE0/0/1 (outbound interface) on the router is, and the IP address of Eth0/0/1 is The remote IP address of GE0/0/1 is Internal users use Easy IP to access the Internet through GE0/0/1. The configuration is as follows: 1. Assign IP addresses to interfaces on the router. [Huawei] interface ethernet 0/0/1 [Huawei-Ethernet0/0/1] ip address 24 [Huawei-Ethernet0/0/1] quit [Huawei] interface gigabitethernet 0/0/1 [Huawei-GigabitEthernet0/0/1] ip address 24 [Huawei-GigabitEthernet0/0/1] quit 2. Configure a default route to ensure that the outbound interface has a reachable route to the remote end. [Huawei] ip route-static 3. Configure NAT on an internal address segment Implement NAT on GE0/0/1 in Easy IP mode. [Huawei] acl number 2000 [Huawei-acl-basic-2000] rule 5 permit source [Huawei-acl-basic-2000] quit [Huawei] interface gigabitethernet 0/0/1 [Huawei-GigabitEthernet0/0/1] nat outbound 2000 [Huawei-GigabitEthernet0/0/1] quit

Configure VRRP on an AR router and connect the router to a firewall for external network access
The roadmap of configuring VRRP on an AR router and connecting the router to a firewall for external network access is as follows: 1. Configure VRRP on an AR router to implement two-node backup, and configure a virtual IP address. 2. Add the Layer 2 interface of a firewall on the intranet side to the same VLAN, and configure a VLANIF address. 3. Add the physical interface and VLANIF interface of the firewall to a security zone, and configure an inter-zone policy. 4. Configure the next hop for the route from the firewall to the intranet as a VRRP virtual IP address so that a normal link can be switched over to if an active link is interrupted. For details about the configuration, see the URL: Example for Connecting the AR to the Firewall Through VRRP.

When the device functions as a PPPoE client, why is the Internet access speed of users on the downstream LAN slow
Run the tcp adjust-mss value command in the dialer interface view to set the MSS of TCP packets on the interface. The recommended value of tcp adjust-mss is 1200 for PPPoE applications. The MTU of the PPPoE-enabled interface is 1492 bytes. When the MTU of outgoing Layer 3 packets on this interface is greater than 1492 bytes and the packets are configured as non-fragmented, packets cannot be sent out. The Internet access speed is slow. You can run the tcp adjust-mss value command on the dialer interface to change the Max Segment Size (MSS) value so that the packet length is smaller than the dialer interface. The packets then can be processed and this problem is solved.

PPPoE dialup service is unavailable and the network access rate is low
Root cause: 1. The AR router is tested. The test result shows that the router can normally forward packets, and the forwarding bottleneck is reached sometimes. 2. According to analysis of obtained packets, the TCP connection has been established and enters the data obtaining phase. However, the device receives RST packets (No. 15136 and No. 15137) from the Internet. As a result, the TCP connection is torn down. Procedure: 1. The networking where the PC is connected to the Internet through the router is tested and services are also abnormal. 2. The networking where the PC is connected to the Internet is tested and no fault occurs. Therefore, the PC works properly. 3. Run the tcp adjust-mss command to set the TCP MSS of the dialup interface to 1400, 1200, or 900. The fault persists. 4. In the networking where the PC is connected to the Internet through the router, services are still abnormal. Run the display health and display interface commands. The command outputs show that the CPU usage and uplink bandwidth usage of the interface are normal, and the interface works in full-duplex mode through negotiation. 5. Run the display fe slot 0 fe-id 0 fwd-status all command to check the packet forwarding status of the device. No severe packet loss occurs. 6. Run the display session number command to check the number of session entries on the device. In peak hours, the number of session entries reaches 16K. 7. Optimize NAT deployment on the intranet interface so that the number of session entries is smaller than the maximum value and users can normally access the Internet.

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