I’ve tried to manually send a ICMP request with a low TTL so see if I get a response.
But nope, VyOS seems to either just ignore it or is unable to send me the answer.
The issues occur when I try to ping from a client.
MTRs and Pings from the VyOS System itself work flawlessly.
(At least to public IPs. Can’t really test internal IPs from the VyOS System, as it has a direct route to each internal VLAN/IP.)
In general, when I have for example an internal route, that should look like that:
Hop 0 - 172.20.100.67 - Client
Hop 1 - 172.20.100.1 - VyOS Router
Hop 2 - 127.20.20.81 - Client on different VLAN
I can manually ping each hop without an issue.
But when I try to do a traceroute to Hop 2 I only see the Hop 2 but not the VyOS router in between.
A more interesting example is:
[yak 72]% traceroute allspice.lcs.mit.edu.
traceroute to allspice.lcs.mit.edu (18.26.0.115), 64 hops max
1 helios.ee.lbl.gov (128.3.112.1) 0 ms 0 ms 0 ms
2 lilac-dmc.Berkeley.EDU (128.32.216.1) 19 ms 19 ms 19 ms
3 lilac-dmc.Berkeley.EDU (128.32.216.1) 39 ms 19 ms 19 ms
4 ccngw-ner-cc.Berkeley.EDU (128.32.136.23) 19 ms 39 ms 39 ms
5 ccn-nerif22.Berkeley.EDU (128.32.168.22) 20 ms 39 ms 39 ms
6 128.32.197.4 (128.32.197.4) 59 ms 119 ms 39 ms
7 131.119.2.5 (131.119.2.5) 59 ms 59 ms 39 ms
8 129.140.70.13 (129.140.70.13) 80 ms 79 ms 99 ms
9 129.140.71.6 (129.140.71.6) 139 ms 139 ms 159 ms
10 129.140.81.7 (129.140.81.7) 199 ms 180 ms 300 ms
11 129.140.72.17 (129.140.72.17) 300 ms 239 ms 239 ms
12 * * *
13 128.121.54.72 (128.121.54.72) 259 ms 499 ms 279 ms
14 * * *
15 * * *
16 * * *
17 * * *
18 ALLSPICE.LCS.MIT.EDU (18.26.0.115) 339 ms 279 ms 279 ms
Note that the gateways 12, 14, 15, 16 & 17 hops away either don't send
ICMP "time exceeded" messages or send them with a ttl too small to
reach us. 14 - 17 are running the MIT C Gateway code that doesn't
send "time exceeded"s. God only knows what's going on with 12.