Return Route Test to China: How to Tell CN2 GIA, CN2 GT, 163, CMI and Unicom 9929 Routes

How fast your site feels in mainland China depends largely on the path your server's traffic takes back into China. This guide explains how to run a return route test to China: run mtr and the open-source nexttrace from the server to China Telecom, China Unicom and China Mobile IPs, read the hop prefixes to identify CN2 GIA, CN2 GT, 163, Unicom 169/9929 or China Mobile CMI, test the forward path from China, and know what to include in a support ticket. Commands work on Debian/Ubuntu and CentOS/Rocky/AlmaLinux.

Step 1: Forward Path vs Return Path

Traffic from China to the server is the forward path; traffic from the server back to China is the return path. The two often differ, and most bulk traffic (web pages, downloads) flows on the return path, so it matters most for perceived speed. Test the forward path from your local PC and the return path from the server.

Step 2: Learn the Common Return Route Hop Prefixes

The IP prefixes that appear in mtr or traceroute tell you which network the traffic is on:

Rule of thumb: a return path that stays on 59.43.* with no 202.97.* is usually CN2 GIA; 202.97.* followed by 59.43.*, or a mix, usually means CN2 GT; only 202.97.* means a standard 163 route. For Unicom, 219.158.* is the standard 169 backbone and 218.105.* typically indicates 9929. For China Mobile, 223.120.* means CMI.

Step 3: Test the Return Route from the Server with mtr

The targets below are public carrier DNS servers used only as examples; if one does not respond, use an IP in your customers' or office's city instead:

# Install mtr
apt install -y mtr-tiny     # Debian/Ubuntu
yum install -y mtr          # CentOS/Rocky/AlmaLinux

# China Telecom
mtr -rwc 30 202.96.209.133   # Shanghai Telecom DNS
mtr -rwc 30 202.96.128.86    # Guangzhou Telecom DNS
# China Unicom
mtr -rwc 30 202.106.0.20     # Beijing Unicom DNS
mtr -rwc 30 210.22.97.1      # Shanghai Unicom DNS
# China Mobile
mtr -rwc 30 211.136.192.6    # Guangdong Mobile DNS
mtr -rwc 30 120.196.165.24   # Guangdong Mobile DNS

For each result look at the middle hop prefixes, plus Avg latency and Loss% at the final hop. Loss at one middle hop that does not continue to later hops is just ICMP rate-limiting and can be ignored.

Step 4: Install the Open-Source nexttrace Tool

nexttrace is an open-source visual traceroute that labels each hop with its ASN and location, which makes the route much easier to read. Its install script is a third-party project, so read it before running:

# Option 1: official install script (third-party open source; download and read first)
curl -sL nxtrace.org/nt -o nt.sh
less nt.sh
bash nt.sh

# Option 2: download the binary for your architecture from GitHub Releases
# https://github.com/nxtrace/NTrace-core/releases

# Trace to an IP (shows ASN and location per hop)
nexttrace 202.96.209.133

# Use TCP 443 probes if the target drops ICMP
nexttrace -T -p 443 202.96.209.133

# Quick test to built-in China Telecom/Unicom/Mobile targets
nexttrace --fast-trace

Step 5: Test the Forward Path from China

From your local computer, trace to the server (replace the example 203.0.113.10 with your server IP). You can also use multi-node online ping and traceroute sites popular in China to test from many provinces and carriers at once:

# Windows: Command Prompt or PowerShell
tracert -d 203.0.113.10
pathping -n 203.0.113.10

# macOS / Linux
mtr -rwc 100 203.0.113.10

Step 6: What to Include in a Support Ticket

• Server IP, plus your local public IP, city and carrier (Telecom, Unicom or Mobile);
• When the problem happens and whether it is only at evening peak;
• Tests in both directions: mtr from the server to your local IP, and mtr or tracert from your side to the server (100+ probes, text or screenshots);
• Which services or ports are affected, e.g. HTTPS 443 or RDP 3389.

FAQ

My return route is CN2 GIA but it is still slow. Why?

The forward path, your local broadband and server load matter too. Test both directions and check whether the server's CPU or bandwidth is maxed out.

Is it normal for the three carriers to get different routes?

Yes. Each carrier peers differently — for example Telecom via CN2 and Mobile via CMI — so latency will also differ.

Can I choose the return route?

Routing is determined by the data center's network policy and differs by product. If you need a specific route, contact us before ordering to confirm the configuration or request a test.

If you still need help, open a support ticket with the results above and the IMIDC 24/7 team will investigate.