Common Troubleshooting Tools¶
RansNet routers include several built-in tools for diagnosing network connectivity, performance, and quality issues. These tools help troubleshoot end-to-end connectivity, measure link quality (latency and packet loss), test throughput, and monitor network performance.
Tool Overview¶
Navigate to Device List, click the yellow Tools button to access the following diagnostic tools:
| Tool | Purpose |
|---|---|
| Ping | Test end-to-end connectivity and measure quality (packet loss, latency) |
| Traceroute | Display the network path and hop-by-hop latency to a destination |
| Throughput Test | Measure data transfer rate using iperf3 (requires remote iperf3 server) |
| Speed Test | Check Internet link speed via cloud-based speed test server |
| TWAMP | RFC 5357 protocol for active network performance measurement (latency, jitter, packet loss) |
| tcpdump | Capture and analyze live network packets to troubleshoot packet flow at each hop |
| Upgrade Firmware | Update device firmware |
| Reboot | Reboot the device |
Ping¶
Ping tests end-to-end connectivity and quality metrics (packet loss, latency, jitter).
GUI Usage¶
Click Ping in the tools menu, enter a destination IP address or FQDN, and click Run.
CLI Usage¶
Enter enable mode and use the ping command:
RansNet# ping 1.1.1.1
source Source IP-address (ip) or interface (ip and arp)
repeat Requests to send count, default is 5
vrf Ping source VRF
resolve Resolve names
broadcast Ping broadcast address
size Packet size
interval The time interval between packets, default is 1
flood Flood ping
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Example¶
RansNet# ping 1.1.1.1 source 10.18.18.1
PING 1.1.1.1 (1.1.1.1) from 10.18.18.1: 56 data bytes
64 bytes from 1.1.1.1: seq=0 ttl=59 time=2.550 ms
64 bytes from 1.1.1.1: seq=1 ttl=59 time=2.176 ms
64 bytes from 1.1.1.1: seq=2 ttl=59 time=2.621 ms
64 bytes from 1.1.1.1: seq=3 ttl=59 time=2.977 ms
64 bytes from 1.1.1.1: seq=4 ttl=59 time=2.683 ms
--- 1.1.1.1 ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max = 2.176/2.601/2.977 ms
RansNet#
Tip
GUI accepts the same options as CLI. Append options directly in the GUI input field (e.g., 1.1.1.1 source 10.18.18.1).
Traceroute¶
Traceroute displays the network path (hops) to a destination and measures the latency between each hop.
GUI Usage¶
Click Traceroute in the tools menu, enter a destination IP address or FQDN, and click Run.
CLI Usage¶
Enter enable mode and use the traceroute command:
RansNet# traceroute
ip IPv4
ipv6 IPv6
String Hostname or IP-address to trace the route
RansNet# traceroute 1.1.1.1
resolve Resolve names
source Source IP-address
vrf Source VRF
interface Source interface
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Example¶
RansNet# traceroute 1.1.1.1
traceroute to 1.1.1.1 (1.1.1.1), 15 hops max, 38 byte packets
1 61.13.198.165 1.146 ms * *
2 10.100.11.245 1.808 ms 1.074 ms 1.291 ms
3 * * *
4 27.111.230.2 1.781 ms 27.111.228.132 1.916 ms *
5 * * 172.69.117.89 4.951 ms
6 1.1.1.1 1.639 ms 2.059 ms *
RansNet#
Note
Hops showing * * * indicate no response (ICMP timeout). This is normal for some intermediate routers.
Speed Test¶
Speed Test measures your Internet link speed by connecting to a cloud-based speed test server (Ookla Speedtest).
GUI Usage¶
Click Speed Test in the tools menu and click Run. The test measures download speed, upload speed, latency, and packet loss.
CLI Usage¶
Use the test speedtest command:
RansNet# test speedtest
Speedtest by Ookla
Server: MyRepublic Singapore - Singapore (id = 5935)
ISP: Sptel
Latency: 1.46 ms (0.78 ms jitter)
Download: 476.84 Mbps (data used: 346.9 MB )
Upload: 938.77 Mbps (data used: 1.3 GB )
Packet Loss: 0.0%
Result URL: https://www.speedtest.net/result/c/08aae5ff-8fd8-43b5-a26d-d15ed264bc2f
RansNet#
Warning
The first time you run this test, you will be prompted to accept the Speedtest license agreement. Enter YES to proceed.
Throughput Test¶
Throughput Test measures data transfer rate using iperf3. It requires an iperf3 server running on a remote system (either a cloud iperf3 server or a RansNet router configured as iperf3 server).
For a list of public iperf3 servers, see iperf.fr.
Architecture¶
RansNet routers can act as either iperf3 server (passive measurement) or client (active measurement). In a point-to-point throughput test:
- Remote RansNet router: runs as iperf3 server
- Local RansNet router: runs as iperf3 client
Step 1: Configure Remote Router as iperf3 Server¶
First, configure the firewall to permit inbound iperf3 traffic:
Then start the iperf3 server:
SGNOC-GW1# test server
-----------------------------------------------------------
Server listening on 5201 (test #1)
-----------------------------------------------------------
Step 2: Run Throughput Test from Client Router¶
Launch the iperf3 throughput test using the test throughput command:
RansNet# test throughput 118.189.175.164
[info] getting download throughput (server send to client).
Connecting to host 118.189.175.164, port 5201
Reverse mode, remote host 118.189.175.164 is sending
[ 4] local 61.13.198.166 port 56496 connected to 118.189.175.164 port 5201
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 48.0 MBytes 402 Mbits/sec
[ 4] 1.00-2.00 sec 46.2 MBytes 388 Mbits/sec
[ 4] 2.00-3.00 sec 56.6 MBytes 476 Mbits/sec
[ 4] 3.00-4.00 sec 58.7 MBytes 492 Mbits/sec
[ 4] 4.00-5.00 sec 57.2 MBytes 480 Mbits/sec
[ 4] 5.00-6.00 sec 57.2 MBytes 480 Mbits/sec
[ 4] 6.00-7.00 sec 57.2 MBytes 480 Mbits/sec
[ 4] 7.00-8.00 sec 57.2 MBytes 480 Mbits/sec
[ 4] 8.00-9.00 sec 57.2 MBytes 480 Mbits/sec
[ 4] 9.00-10.00 sec 56.9 MBytes 477 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth Retr
[ 4] 0.00-10.00 sec 558 MBytes 468 Mbits/sec 609 sender
[ 4] 0.00-10.00 sec 553 MBytes 464 Mbits/sec receiver
iperf Done.
[info] getting upload throughput (client send to server).
Connecting to host 118.189.175.164, port 5201
[ 4] local 61.13.198.166 port 56574 connected to 118.189.175.164 port 5201
[ ID] Interval Transfer Bandwidth Retr Cwnd
[ 4] 0.00-1.00 sec 16.1 MBytes 135 Mbits/sec 27 252 KBytes
[ 4] 1.00-2.00 sec 15.8 MBytes 133 Mbits/sec 1 221 KBytes
[ 4] 2.00-3.00 sec 15.7 MBytes 132 Mbits/sec 5 190 KBytes
[ 4] 3.00-4.00 sec 15.5 MBytes 130 Mbits/sec 0 247 KBytes
[ 4] 4.00-5.00 sec 15.9 MBytes 134 Mbits/sec 1 220 KBytes
[ 4] 5.00-6.00 sec 15.6 MBytes 131 Mbits/sec 6 187 KBytes
[ 4] 6.00-7.00 sec 15.9 MBytes 133 Mbits/sec 0 244 KBytes
[ 4] 7.00-8.00 sec 16.0 MBytes 134 Mbits/sec 13 204 KBytes
[ 4] 8.00-9.00 sec 15.7 MBytes 132 Mbits/sec 0 258 KBytes
[ 4] 9.00-10.00 sec 15.6 MBytes 131 Mbits/sec 1 232 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth Retr
[ 4] 0.00-10.00 sec 158 MBytes 132 Mbits/sec 54 sender
[ 4] 0.00-10.00 sec 157 MBytes 132 Mbits/sec receiver
iperf Done.
RansNet#
TWAMP¶
TWAMP (Two-Way Active Measurement Protocol) is a standards-based protocol defined in RFC 5357 for actively measuring IP network performance metrics (latency, jitter, packet loss) between two endpoints.
RansNet routers can function as either TWAMP server (responder) or client (initiator).
Step 1: Enable TWAMP Server on Remote Router¶
Start the TWAMP server:
SGNOC-GW1# twping server start
Starting twamp-server (via systemctl): twamp-server.service.
SGNOC-GW1#
Configure firewall rules to permit TWAMP traffic:
- TCP port 862 (control channel)
- UDP ports 18760-19960 (data channels)
Server mode options:
# Start server on default port 862
twping server start
# Start on custom port
twping server start port 5000
# Start on specific address
twping server start address 192.168.1.1
# Check server status
twping server status
# Stop server
twping server stop
# Shorthand (start is default)
twping server
Step 2: Run TWAMP Client on Test Router¶
Launch the TWAMP client test:
VM53-Demo-Data1# twping client 118.189.175.164
Session ID: 76bdafa4edbc59aa939ab58df0c46b82
76bdafa4edbc59aa939ab58df0c46b82
Time: 2026-05-24T00:51:55.704 - 2026-05-24T00:52:03.827
Stats: 100 sent, 0 lost (0.000%), 0 send duplicates, 0 reflect duplicates
===================================================================
Direction Min Max Avg Jitter Loss
-------------------------------------------------------------------
Send (outbound): 0.0582ms 2.72ms 0.3ms 0.6 0.000%
Reflect (inbound): 0.128ms 2.15ms 0.3ms 0.2 0.000%
Roundtrip: 0.186ms 3.1ms 0.6ms 1.4 0.000%
-------------------------------------------------------------------
VM53-Demo-Data1#
Client mode options:
# Basic client test
twping client 118.189.175.164
# With custom count
twping client 118.189.175.164 repeat 200
# With source IP/interface
twping client 118.189.175.164 source 192.168.1.1
# With authentication
twping client 118.189.175.164 username testuser
# Combined
twping client 118.189.175.164 repeat 200 source eth0 username testuser
tcpdump¶
tcpdump captures live network packets for detailed traffic analysis. Use it to observe packet flows at each hop in the network path and identify where traffic is being dropped or blocked.
RansNet routers include tcpdump pre-installed. Run it on an interface to see live packets:
RansNet# tcpdump interface eth0 port 443
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
13:10:04.814948 IP 61.13.198.166.59874 > 118.189.175.168.443: Flags [S], seq 2132128584, win 29200, options [mss 1460,sackOK,TS val 73030990 ecr 0,nop,wscale 6], length 0
13:10:04.820498 IP 61.13.198.166.37762 > 118.189.175.168.443: Flags [P.], seq 3045555367:3045555884, ack 3162549609, win 457, length 517
13:10:04.820984 IP 118.189.175.168.443 > 61.13.198.166.59874: Flags [S.], seq 1045307433, ack 2132128585, win 42340, options [mss 1460,nop,nop,sackOK,nop,wscale 9], length 0
13:10:04.824429 IP 61.13.198.166.59874 > 118.189.175.168.443: Flags [.], ack 1, win 457, length 0
13:10:04.824680 IP 61.13.198.166.59874 > 118.189.175.168.443: Flags [F.], seq 1, ack 1, win 457, length 0
13:10:04.824912 IP 61.13.198.166.59874 > 118.189.175.168.443: Flags [R.], seq 2, ack 1, win 457, length 0
13:10:04.828595 IP 118.189.175.168.443 > 61.13.198.166.37762: Flags [.], ack 517, win 83, length 0
13:10:04.898689 IP 61.13.198.166.51570 > 13.204.106.34.443: Flags [.], ack 4108510905, win 251, length 0
CLI Usage¶
RansNet# tcpdump interface eth0 port 443
host View output by specific source or destination host
filter Filter output by expression (e.g., src 192.168.1.1)
detail Display full packet details (header and payload)
vrf Run tcpdump within a specific VRF
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Example: Troubleshooting Packet Flow¶
When packets aren't reaching their destination, use tcpdump at each hop to identify where they're being dropped or blocked. Follow this decision tree:
flowchart TD
A["Run tcpdump on incoming interface<br/>(expected source side)"] --> B{"Packets<br/>arriving?"}
B -->|No| C["Check upstream routing<br/>and accessibility"]
B -->|Yes| D["Run tcpdump on outgoing interface<br/>(expected destination side)"]
D --> E{"Packets<br/>leaving?"}
E -->|No| F["Check:<br/>• Firewall rules permit access?<br/>• Routing table has route<br/>to destination?"]
E -->|Yes| G{"Receiving<br/>reply packets?"}
G -->|No| H["Check:<br/>• Firewall rules for return traffic<br/> (SNAT/translation)?<br/>• Upstream routing has route<br/> back to source IP?"]
G -->|Yes| I["Check downstream device<br/>(next-hop router/firewall)<br/>blocking return path"]
C --> J["Problem found on<br/>upstream path"]
F --> K["Problem found on<br/>local router"]
H --> L["Problem found on<br/>upstream path"]
I --> M["Problem found on<br/>downstream path"]
style J fill:#ffcccc
style K fill:#ffcccc
style L fill:#ffcccc
style M fill:#ffccccTroubleshooting methodology:
- Incoming interface — Verify traffic arrives from the source. Use filters (e.g.,
host 192.168.1.1) to isolate specific flows. -
If packets don't arrive, the problem is upstream (check routing and reachability to your router).
-
Outgoing interface — Verify traffic leaves toward the destination.
-
If packets don't leave, check local firewall rules and routing table.
-
Return packets — Verify replies come back.
-
If no replies arrive, check firewall translation rules (SNAT) and upstream routing for the reverse path.
-
Repeat on each hop — Walk through each router/firewall in the end-to-end path using the same method. This narrows the problem to a specific device.
Repeat the same approach on each hop/router in between the end-to-end path, you can easily isolate to the "problem" hop/router and discover the root cause.