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by sulandor 658 days ago
seems like clickbait

traceroute uses udp to a high-port for discovery, not icmp-echo.

4 comments

I agree that this doesn’t seem to have been written by someone that actually understands the topic.

Even the network diagram at the beginning is not very good. Can you create network architectures where 10.0.0.1 and 10.0.0.2 are not layer 2 adjacent? Yes, but they’re fairly complex and would imply that a lot of other necessary information is missing from the diagram. And should you use such an architecture as an example to explain traceroute? Absolutely not. It’s hard to imagine someone with even a CCNA level understanding of networking coming up with this.

Glad I'm not the only one who was bothered by this. No subnet masks in the diagram, and I'm supposed to assume that 10.0.0.1 and 10.0.0.2 are not in the same broadcast domain. So my default gateway is what, 10.0.0.0, and that router has a route to 10.0.0.2/? with a next-hop of 10.1.0.5?

Wackiest network I've seen in a while, and I've seen some real winners.

/31 linknets are common in the ISP world, it might even be /32 loopback of those devices, who knows.

I do agree that its bad but not for the same reason. On the diagram it looks like router IPs are their loopback IPs rather than the link IP, as we know a traceroute response comes from the interface the packet came in and that IP is used in the response. Seems like the creator tried to simplify the diagram and excluded linknets but made it more confusing instead.

Windows tracert uses ICMP

Source: https://support.microsoft.com/en-gb/topic/how-to-use-tracert...

> The TRACERT diagnostic utility determines the route to a destination by sending Internet Control Message Protocol (ICMP) echo packets to the destination

true, most computers don't run windows though.

anyways, the type of packet does not really matter.

traceroute supports multiple protocols, not just UDP and ICMP.
true, the type of packet does not really matter.

my apologies if this misconstrued my point about the lacking quality of the article.

As a firewall-admin this comment really annoys me.

Heres why: Lots of calls from people complaining their application is not working because the network is broken. Look! at! this! traceroute! supporting! my! complaint!!!

Yeah, it is because udp from any to any is blocked on the firewall for good reasons while icmp traceroute is open. And be carefull because -I specifies the outgoint interface on some os, not the use of ICMP.

most applications don't run over icmp so it is indeed sensible to not use it as a default.