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doc-exports/docs/natgw/umn/nat_faq_0017.html
Qin Ying, Fan 139ab2d266 NATGW UMN 20230525 version 
Reviewed-by: Hasko, Vladimir <vladimir.hasko@t-systems.com>
Co-authored-by: Qin Ying, Fan <fanqinying@huawei.com>
Co-committed-by: Qin Ying, Fan <fanqinying@huawei.com>
2023-08-13 18:20:51 +00:00

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What Should I Do If the Remote Server Fails to Be Accessed Through the NAT Gateway?

If your TCP connection fails when your ECS is accessing a server on the public network through an SNAT rule, perform the following steps:

  1. Run the following command to check whether tcp_tw_recycle is enabled on the remote server:

    sysctl -a|grep tcp_tw_recycle

    If the value of tcp_tw_recycle is 1, tcp_tw_recycle is enabled.

  2. Run the following command to check the number of lost packets of the remote server:

    cat /proc/net/netstat | awk '/TcpExt/ { print $21,$22 }'

    If the value of ListenDrops is not 0, packet loss occurs, that is, the network is faulty.

Troubleshooting

Method 1: Modifying the kernel parameter of the remote server

  • Run the following command to temporarily modify the parameters (the modification becomes invalid after the server is restarted):

    sysctl -w net.ipv4.tcp_tw_recycle=0

  • Perform the following operations to permanently modify the parameters:
    1. Modify the /etc/sysctl.conf file:

      vi /etc/sysctl.conf

      Add the following content to the file:

      net.ipv4.tcp_tw_recycle=0

    2. Press Esc, enter :wq!, and save the file and exit.
    3. Run the following command to make the modification take effect:

      sysctl -p

Method 2: Modifying the kernel parameter of the local client

  • To temporarily modify parameters (the settings become invalid after the local client is restarted), configure the parameter as follows:

    sysctl -w net.ipv4.tcp_timestamps=0

  • Perform the following operations to permanently modify the parameters:
    1. Modify the /etc/sysctl.conf file:

      vi /etc/sysctl.conf

      Add the following content to the file:

      net.ipv4.tcp_timestamps=0

    2. Press Esc, enter :wq!, and save the file and exit.
    3. Run the following command to make the modification take effect:

      sysctl -p

Parent topic: SNAT