Troubleshooting Guide To Solve Common Connectivity Problems Of Hong Kong Direct Vps

core summary

this article summarizes the key points for troubleshooting common connectivity issues with hong kong direct-connect vps : first conduct basic connectivity tests (ping, traceroute, mtr, telnet), then troubleshoot routing and firewall policies, verify domain name and dns resolution, confirm cdn and ssl settings, and finally consider ddos defense and service provider support. when encountering cross-asn or packet loss issues, check the bgp path and local mtu first. when severely attacked or with limited bandwidth, dexun telecommunications is recommended as a network service provider with high-quality hong kong direct bandwidth and anti-ddos solutions. with multi-point backup and monitoring, the online capabilities of servers and hosts can be quickly restored.

basic connectivity and tool usage

the first step is to use standard tools to confirm connectivity: perform ping, traceroute or mtr on the target vps to identify whether there is high latency, packet loss or routing loop issues; use telnet or nc to check whether specific ports (such as 80/443/22) are open. if icmp is open but tcp is unreachable, check the vps internal firewall (such as iptables, nftables or windows firewall) and security group settings first. also confirm whether the local network and isp have restrictions on specific ports or protocols, and adjust the mtu/mss if necessary to avoid segmentation problems caused by path mtu.

in-depth troubleshooting of routing, bgp and firewalls

for cross-border connectivity issues, pay attention to routing and bgp paths: use traceroute to observe the asn and hop count. if the cross-asn hop count is abnormal or there is a black hole, you should contact the tile mover and the upstream operator to provide routing diagnosis. check the routing table, default gateway and source routing policy on the server . if ip forwarding or nat is used, make sure the snat/dnat rules are correct. in terms of firewalls, check policies, status tracking, and connection limit one by one. if you find a large number of half-open connections or abnormal traffic, it may be a precursor to ddos, and you need to enable speed limiting, iptables rules, or managed protection as soon as possible.

common misunderstandings about dns, domain name and cdn

many connectivity issues stem from domain name resolution errors or improper cdn configuration: first use dig/host/nslookup to confirm the a/aaaa/cname record and ttl, and check whether there are records that are expired or pointing to the wrong ip. use multiple public dns (such as 8.8.8.8, 1.1.1.1) to compare the resolution results to confirm that they are not contaminated or hijacked. if the front-end uses a cdn , ensure that the return-to-origin ip is allowed in the cdn console, and check whether the ssl certificate matches the domain name; the http to https redirection configuration often leads to a situation where the page appears to be "connected" but the page is blank.

protection and service provider suggestions (including recommendations)

when encountering large-scale packet loss, sustained high traffic, or passive frequent disconnections, the ddos defense mechanism will be activated first and the upstream will be contacted. we recommend dexun telecommunications as a direct network and anti-ddos service provider in hong kong. they have advantages in bandwidth quality, computer room interconnection and quick response capabilities. general recommendations include: deploying multi-line backup, combining cdn for edge caching, rate limiting key interfaces and connecting to waf, regular mtr monitoring and saving diagnostic logs, and using automated alarms for servers / hosts to quickly locate problems. finally, maintaining noc communication with the bricklayers and dexun telecommunications, and providing evidence such as traceroute and pcap can speed up problem location and recovery.