Cn2 Hong Kong’s Backhaul Route Identification And Isp Cooperation And Communication Skills

1. purpose: confirm whether the path (return) of the data packet from the target to the local area passes through cn2 hong kong or is hijacked/circuited. small segments: a) slow return/packet loss is not necessarily related to the local export; b) cn2 is generally on the advanced channel of china unicom/telecom, and identification can determine whether you can enjoy cn2 quality.

2. tools: linux/mac/windows host, mtr/traceroute/tracert, tcptraceroute (or use hping3), tcpdump, looking glass, bgp query (bgp.he.net) and ssh. small segments: a) administrator rights are required to capture packets; b) prepare the public ip, test target ip (hong kong export) and time window.

3. steps: a) run mtr -rwz target ip (or traceroute -t -p 443 target ip) locally and record the delay and packet loss; b) do the same measurement on the target end (such as the server or the other party supports it) and compare the two-way differences. small segment: description: traceroute using tcp port 443 is closer to the actual traffic path, udp/icmp is sometimes dropped.

4. steps: a) use icmp, udp, and tcp (443/80) to do traceroute respectively; b) use tcptraceroute or hping3 to specify the source port and destination port to detect the impact of the firewall. small segmentation: if tcp goes to cn2 but icmp does not go, it means that icmp cannot make the only decision.

5. steps: a) perform traceroute on looking glass in multiple regions (especially mainland china, hong kong, and neighboring countries), and record the as number and ip of each hop; b) use bgp.he.net or whois to query the as ownership of each hop. small segmentation: by comparing the path differences of different exits, it can be determined whether the return journey takes the cn2 link or is traced back to the public network cleaning point.

6. steps: a) use tcpdump -i any port 443 -w cap.pcap on the edge router/server to capture packets; b) open it with wireshark to see if there is an mpls label (sometimes displayed as mpls or label stack). small segmentation: mpls label, ttl behavior and intermediate as display can directly prompt whether the data has entered the cn2 dedicated line.

7. steps: a) summarize the traceroute/mtr output (with timestamps, commands and parameters); b) attach tcpdump packet capture fragments, bgp route display diagrams, as number whois results, and comparison screenshots in the two directions; small segments: mark the key jump points in red and indicate the suspicion points (such as a certain high jump packet loss/a certain as that does not belong to cn2) to facilitate isp's quick positioning.

8. steps: a) the title should be concise: for example, "[emergency] cn2 hong kong backhaul packet loss/delay - test time/source ip/destination ip"; b) the text includes reproduction steps, measurement results, and expectations (such as restoring cn2 backhaul or troubleshooting an as); c) attach evidence files and recommended check items (bgp tables, mpls labels, routing policies). small segment: it is recommended to put forward the specific operations you want in the work order: for example, ask the other party to perform tcpdump at its boundary, check the bgp egress policy, and check the community/route mapping.

9. steps: a) if there is no response to the work order, communicate on the phone and quote the work order number and key measurement points; b) request to arrange real-time consultation with the other party's network engineer, and both parties will perform traceroute and packet capture at their respective edges at the same time; c) if the other party is a third-party operator, ask the other party to contact the upstream and share the bgp convergence log. small segments: maintaining a technical tone and providing reproducible steps and time windows will significantly improve isp response efficiency.

10. answer: cross-verification through multiple methods: a) the as number displayed by traceroute/mtr belongs to china unicom/cn2 related as; b) mpls label or specific ttl behavior appears in wireshark packet capture; c) the same path can be seen on china unicom/telecom's looking glass. if all three items are true, it can basically be confirmed that it is a cn2 return trip.

11. answer: use evidence to upgrade the level first: a) attach clear test data and timestamp to the work order and request internal upgrade; b) if it is invalid, request a conference call or submit it to the isp's technical manager/poc; c) at the same time, open an information request to the upstream or peer isp (if the as can be identified), and let the other party help check the bgp policy.

12. answer: yes. the recommended template includes: title (urgency level + problem description), time window, source ip/destination ip, command and output (mtr/traceroute/tcptraceroute), packet capture file, suspected jump points and recommended check items (bgp/acl/mpls), desired response time and contact information. package the attachments and list the key points in the main text for quick location.