Asterix in the traceroute

Question

I'm having a bit of trouble getting my routing right.

I have an HP v1910 switch with a a few VLAN interfaces. Let's take the first VLAN, VLAN10, which runs all my laptops etc... All VLANs connect via a trunk port to my router (Draytek Vigor 2920).

In my routing table I have a route that successfully sends data out to the internet. I know it works because I can access the internet. However, when trying to run a traceroute, I get the first IP (my VLAN interface) then *'s followed by my ISPs gateway IP address. I cannot work out why - I even SSH'd into the router and enabled ICMP echoing.

Surely the router should show up in my traceroute?

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score 3 · Answer 1 · edited Apr 13 '17 at 12:57

3

traceroute (on *NIX systems) is using UDP to send out messages and the answers are icmp time exceeded. If your router dose not send these (or you block them on your side) you'll only see *. . tracert on Windows uses ICMP to send out packets. On *NIX you can switch to ICMP by using traceroute -I.

Another reason you may see * in a traceroute is that the router is just to busy sending out ICMP messages.

I already explained traceroute in more detail here

edited Apr 13 '17 at 12:57

Community

1

answered Apr 10 '15 at 18:45

The router *used* to show up. I've just checked all the syslogs and not seen any other problems. – CircularRecursion Apr 10 '15 at 19:28
If you can capture network traffic on your router (e.g. by using tcpdump) see what happening.. – Apr 10 '15 at 20:11

Asterix in the traceroute

1 Answers1