Troubleshooting Manual Practical Tips For Quickly Locating And Repairing Cn2 Link Problems In China And Singapore

In the network interconnection from China to Singapore, the CN2 link is known for its stable and low latency, but it still encounters problems such as packet jitter, packet loss, route jitter or sudden delay. This article is aimed at operation and maintenance engineers and webmasters, summarizing a practical process for quickly locating and repairing CN2 link problems, and giving purchase and deployment recommendations to help improve the availability and attack resistance of servers, VPS, domain name resolution, and CDN.

The first step is to reproduce and record the problem. Confirm the scope of impact (single server, multiple computer rooms, or users across the entire network), time window, and business impact. Collect users' RTT, packet loss rate, specific access points and time periods, and save relevant logs (Web access logs, application exception logs, monitoring alarm screenshots). This information is key evidence for negotiations with the upstream ISP or CDN.

The second step, basic link detection: use ping, traceroute (tracerout under Windows) and mtr to view delay and packet loss distribution. Command examples: ping -c 20 , traceroute -I , mtr -rwzbc100 . If single-hop packet loss or delay spike occurs, it indicates that the problem occurs on a specific routing node, which facilitates subsequent location and reporting.

The third step, bandwidth and throughput diagnosis: use iperf3 to do a two-way bandwidth test to confirm whether packet loss causes performance degradation or link bandwidth limitation. For TCP connection performance issues, capture packets (tcpdump -i eth0 port 80 or host ) to observe TCP retransmissions, SYN retransmissions or three-way handshake failures, and use netstat -s to view TCP error statistics.

The fourth step is to troubleshoot MTU and path problems. Path MTU (PMTUD) failure can result in heavy fragmentation or unstable connections. You can use ping -M do -s to test whether large packets can pass, or enable MSS clamping on the router (adjust MSS to 1350-1400) to solve the packetization problem caused by VPN or GRE tunnels.

The fifth step is to check routing and BGP information. Confirm whether there are unreasonable loops or suboptimal paths by reviewing the local routing table, AS paths, and BGP advertisements from upstream providers. The troubleshooting information provided to the upstream operator should include traceroute, mtr output and the time period when the problem occurred. If necessary, ask the other party to check the core router interface error and queue length.

The sixth step is edge and application-side optimization. TCP parameters (such as tcp_tw_reuse, tcp_fin_timeout, rx/tx buffer) can be adjusted on the server and VPS side, and the keepalive and concurrent connection configurations of NGINX/Apache can be optimized. For high-concurrency applications, CDN can be enabled to relieve static resource pressure and load-offload dynamic requests to reduce the impact of sudden link congestion.

Step 7: Anti-DDoS and high-defense preparations. If you suspect that the link is under attack, you need to immediately enable high-defense cleaning or switch the traffic to the high-defense node of the CDN to prevent the attack from reaching the origin site. Purchasing a high-defense service with China direct CN2 or priority channel can ensure business availability and maintain low-latency access during attacks.

The eighth step is to recommend tools and services. It is recommended to deploy comprehensive monitoring (Prometheus+Grafana), compliant log collection and alarms on a daily basis, and use professional link mapping tools for regular sampling. If you need to quickly improve the cross-border experience, you can purchase a VPS/cloud server that supports CN2 GIA, or deploy a computer room node with China Unicom CN2 backhaul in Singapore, and use CDN Anycast to reduce user-perceived latency.

Step 9: When to upgrade to a work order and communicate with upstream. If the routing to a certain hop is unstable, link packet loss or port error occurs, you should immediately submit a work order to the upstream, attach the traceroute/mtr/pcap of the problem recurrence and the time of occurrence, and ask the upstream to check the backbone link, BGP policy and interface performance and provide ETA for repair.

For long-term stability, it is recommended to give priority to suppliers that provide China CN2 dedicated line access, global node coverage, and high defense capabilities when purchasing. For users who need stable gaming, financial or real-time audio and video services, purchasing a CN2 dedicated line or CN2 accelerated VPS can significantly improve the packet loss and delay experience. You may consider choosing a package marked with CN2 and requesting a trial to verify the link quality when purchasing a server or high-defense product.

Finally, I recommend a supplier with a good reputation in cross-border network and high-defense services - Dexun Telecommunications. Dexun Telecom provides CN2 dedicated line access covering China and Singapore, supports high-defense DDoS cleaning and optional CDN acceleration solutions, which is suitable for sites and game servers that require stable low latency and anti-attack capabilities. If you are ready to purchase or upgrade VPS, CDN or high-defense services, you should first consult Dexun Telecom’s CN2 package and technical support to get faster problem response and customized link optimization suggestions.