Traceroute works but ping does not

Question

My immediate goal is to ping from a device on my LAN to a Ubuntu 22.04 on WSL2.

Context

I am learning to use ROS2. It allows communication between instances on different machines through FastDDS. Once it is setup it should be fairly convenient. Since I don't know how to set it up in my environment I asked FastDDS: demo_nodes_cpp between WSL2 and Raspberry Pi. To summarize: FastDDS did not work by default, so I started researching how to make it work. The conversation linked above lead to me circumventing the default way of discovering other ROS2 instances and instead configuring a discovery server. This works, but now I want to find a solution without using a WireGuard VPN. I believe this to be possible with the correct settings. I hope that this might also be a way to find out how to route multicast packages.

Status Quo

I have a RasPi running Ubuntu 22.04 connected via WiFi on the subnet 192.168.178.0/24 with IP address 192.168.178.21.

My Windows 10 PC has the IP 192.168.178.51.

The WSL2 exposes its adapter with the address 172.27.112.1 on subnet 172.27.112.0/20. The Ubuntu 22.04 running on WSL2 has the address 172.127.124.243.

At 192.168.178.1 runs my fritz.box router. I have configured it to route 172.27.112.0/20 through gateway 192.168.178.51. Pinging from 192.168.178.21 to 172.27.112.1 works:

[192.168.178.21]$ ping 172.27.112.1
  PING 172.27.112.1 (172.27.112.1) 56(84) bytes of data.
  From 192.168.178.1 icmp_seq=1 Redirect Host(New nexthop: 192.168.178.51)
  64 bytes from 172.27.112.1: icmp_seq=1 ttl=127 time=5.46 ms
  ...

However, pinging from 192.168.178.21 to 172.27.124.243 does not work:

[192.168.178.21]$ ping 172.27.124.243
  PING 172.27.124.243 (172.27.124.243) 56(84) bytes of data.
  From 192.168.178.1 icmp_seq=1 Redirect Host(New nexthop: 192.168.178.51)
  ^C
  --- 172.27.124.243 ping statistics ---
  5 packets transmitted, 0 received, +1 errors, 100% packet loss, time 4063ms

This confuses me, since traceroute from 192.168.178.21 to 172.27.124.243 works:

[192.168.178.21]$ traceroute 172.27.124.243
  traceroute to 172.27.124.243 (172.27.124.243), 30 hops max, 60 byte packets
   1  DESKTOP-XXXXXXX.fritz.box (192.168.178.51)  1.925 ms * *
   2  172.27.124.243 (172.27.124.243)  3.348 ms  2.353 ms  3.321 ms

Even more so since I can ping from 192.168.178.51 to 172.27.124.243:

[192.168.178.51]$ ping 172.27.124.243
Pinging 172.27.124.243 with 32 bytes of data:
  Reply from 172.27.124.243: bytes=32 time<1ms TTL=64
  ...

Also, the ping in the other direction from 172.27.124.243 to 192.168.178.21 works:

[172.27.124.243]$ ping 192.168.178.21
  PING 192.168.178.21 (192.168.178.21) 56(84) bytes of data.
  64 bytes from 192.168.178.21: icmp_seq=1 ttl=63 time=98.6 ms
  64 bytes from 192.168.178.21: icmp_seq=2 ttl=63 time=2.19 ms

I have read that traceroute does not ECHO responses on superuser but but this still leaves me clueless.

Edit: Firewall on 172.27.124.243:

[172.27.124.243]$ sudo iptables -L
  [sudo] password for user:
  Chain INPUT (policy ACCEPT)
  target     prot opt source               destination
  ACCEPT     icmp --  anywhere             anywhere             icmp   echo-request
Chain FORWARD (policy ACCEPT)
  target     prot opt source               destination
Chain OUTPUT (policy ACCEPT)
  target     prot opt source               destination

On Windows, I have configured the firewall to allow all incoming ICMPv4 packages. Although this should not impact ping on other machines. I have also set Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\IPEnableRouter to 1.

Questions

Why does traceroute 'work' but ping not?
How can I fix this?
What do I need to change in my configuration to make discovery (FastDDS) work with multicast on my network?

Traceroute works but ping does not

0 Answers0