Use Traceroute to Diagnose Network Issues

Traceroute maps the sequence of gateways a packet crosses on its way from your PBX to a destination host. Because it shows each router along the path and how long each hop takes, it is a fast way to confirm that a host is reachable and to pinpoint where a connection is stalling or dropping. The tool is built into the web portal, so you can run it directly from the PBX.

Run a traceroute

1. Sign in to the PBX web portal and go to Maintenance > Troubleshooting > Traceroute.
2. In the Target Host field, type the domain name or IP address you want to reach.
3. Click Start. The PBX begins tracing the route to the target.
4. Let the trace finish on its own, or click Stop to end it early. It also stops automatically once it reaches the destination or the maximum hop count.

Interpret the results

The trace opens with two summary lines before the per-hop detail begins. The first line, start..., simply marks the start of the run. The second line names the target you entered, the IP address it resolved to, the maximum number of hops the trace will attempt (30), and the size of each probe packet (46 bytes). Every line after that describes one hop and follows this pattern:

HOP  Domain Name (IP Address)  RTT1  RTT2  RTT3

• HOP: Every time a packet is handed off between routers, that step counts as one hop. The hop number at the far right of the trace (before it reaches the target) tells you how many routers separate the PBX from the destination.
• Domain Name (IP Address): The router at that hop. When a reverse DNS name is available it appears alongside the IP and often hints at the router’s location; otherwise only the IP address is shown.
• RTT1, RTT2, RTT3: The round-trip time (RTT), in milliseconds, for a packet to reach that hop and return. This is the same latency figure you get from ping. Traceroute probes each hop three times so you can gauge how steady the latency is. An asterisk (*) in place of a time means no reply was received for that probe, which can point to packet loss.

Note

A router showing * * * has not answered the traceroute probes, but that does not always mean a problem. Many routers are configured to forward traffic while ignoring these requests, so a hop can appear unresponsive and still pass packets to the next hop.

Example 1: A healthy path

In the trace below, the destination is reached and round-trip times stay reasonable throughout. Several early hops answer with * * * yet still forward traffic to the next router, so the path is intact.

start...
traceroute to www.example.com (36.152.44.95), 30 hops max, 46 byte packets
 1  *  *  *
 2  *  *  *
 3  192.168.1.1 (192.168.1.1)  1.853 ms  11.642 ms  19.951 ms
 4  110.80.36.161 (110.80.36.161)  3.008 ms  2.966 ms  3.943 ms
 5  61.154.238.133 (61.154.238.133)  7.369 ms  27.982 ms  7.808 ms
 6  117.30.27.177 (117.30.27.177)  6.125 ms  117.30.24.213 (117.30.24.213)  4.664 ms  4.376 ms
 7  202.97.36.117 (202.97.36.117)  26.446 ms  202.97.64.178 (202.97.64.178)  22.534 ms  202.97.79.33 (202.97.79.33)  20.897 ms
 8  202.97.63.18 (202.97.63.18)  33.276 ms  202.97.76.238 (202.97.76.238)  36.685 ms  202.97.18.46 (202.97.18.46)  33.961 ms
 9  *  *  *
10  *  *  *
11  *  *  *
12  *  *  *
13  *  *  *
14  221.183.14.14 (221.183.14.14)  40.599 ms  221.183.18.2 (221.183.18.2)  54.233 ms
15  183.207.22.21 (183.207.22.21)  43.056 ms  53.602 ms  50.481 ms
16  183.207.23.122 (183.207.23.122)  47.251 ms  183.207.23.126 (183.207.23.126)  47.401 ms  183.207.23.110 (183.207.23.110)  54.380 ms
17  *  *  *
18  *  *  *
19  *  *  *
20  *  *  *
21  *  *  *
22  *  *  *
23  202.97.23.149 (202.97.23.149)  14.133 ms  *  202.97.23.157 (202.97.23.157)  28.851 ms
24  61.154.238.69 (61.154.238.69)  7.096 ms  117.30.24.213 (117.30.24.213)  4.682 ms  117.30.27.189 (117.30.27.189)  2.758 ms
25  113.96.4.170 (113.96.4.170)  14.663 ms  113.96.5.118 (113.96.5.118)  17.857 ms  113.96.4.190 (113.96.4.190)  20.665 ms
26  *  *  *
27  *  *  *
28  *  *  *
29  110.80.36.161 (110.80.36.161)  4.278 ms  2.696 ms  3.900 ms
30  61.154.238.133 (61.154.238.133)  11.424 ms  4.690 ms  7.770 ms

Example 2: A path that breaks off

Here the trace resolves the target and answers cleanly through hop 10, then returns * * * for every hop from 11 onward until it hits the 30-hop limit. When responses stop at one point and never resume, the connection is failing somewhere past the last hop that replied, so that is where to focus your investigation.

Caution

A trace that shows * * * for every remaining hop up to the 30-hop limit does not always mean the host is unreachable. Many destination servers and firewalls silently drop traceroute probes for security while still accepting real traffic such as SIP (the protocol that carries calls) or HTTPS. Before you conclude the path is down, confirm the outage another way, for example by testing the actual service.

Tip

When a trace fails, look at the last hop that answered. If its address is a private one (for example 192.168.x.x, 10.x.x.x, or 172.16.x.x through 172.31.x.x), the break is inside your own network and is yours to fix. If the last good hop is a public address, the fault is upstream at your internet provider or a carrier along the route, and you will likely need to open a ticket with them.

start...
traceroute to www.example.com (14.215.177.38), 30 hops max, 46 byte packets
 1  *  *  *
 2  *  *  *
 3  192.168.1.1 (192.168.1.1)  1.702 ms  4.912 ms  1.873 ms
 4  110.80.36.161 (110.80.36.161)  16.068 ms  2.642 ms  2.705 ms
 5  61.154.238.129 (61.154.238.129)  5.405 ms  61.154.238.133 (61.154.238.133)  9.038 ms  61.154.238.129 (61.154.238.129)  4.084 ms
 6  117.30.27.185 (117.30.27.185)  3.183 ms  117.30.24.213 (117.30.24.213)  5.256 ms  29.543 ms
 7  202.97.19.125 (202.97.19.125)  23.899 ms  202.97.23.153 (202.97.23.153)  15.059 ms  202.97.21.69 (202.97.21.69)  12.542 ms
 8  113.96.4.130 (113.96.4.130)  20.978 ms  113.96.4.54 (113.96.4.54)  17.600 ms  113.96.4.102 (113.96.4.102)  18.980 ms
 9  113.96.4.209 (113.96.4.209)  18.324 ms  25.160 ms  219.135.96.106 (219.135.96.106)  29.135 ms
10  14.29.117.242 (14.29.117.242)  22.918 ms  121.14.67.150 (121.14.67.150)  15.187 ms  14.215.32.126 (14.215.32.126)  15.963 ms
11  *  *  *
12  *  *  *
13  *  *  *
14  *  *  *
15  *  *  *
16  *  *  *
17  *  *  *
18  *  *  *
19  *  *  *
20  *  *  *
21  *  *  *
22  *  *  *
23  *  *  *
24  *  *  *
25  *  *  *
26  *  *  *
27  *  *  *
28  *  *  *
29  *  *  *
30  *  *  *