Network routing issue

Posted: Tue Dec 13, 2011 11:33 am Post subject: Network routing issue

Hi guys, just wondering if we have a network guru here who can illuminate an issue we are having. Andrew and Darryl have been brilliant in getting us to the point we are but the issue is really out of their control.

We are accessing NetHosted services from Canada, so there is a transatlantic hop. From one location here we have a mixed network of Windows and one Linux server. When we do a traceroute from this network to our site on NH we get two different results. The Windows machine goes one way and the Linux box goes another.

The issue starts at step 12 from requests from Linux:

12 69.63.248.89
13 if-3-0.icore1.NTO-NewYork.as6453.net

but the windows boxes go from
69.63.248.89 to
if-9-0.icore2.NTO-NewYork.as6453.net

and follow a different path from there.

The question is, is it not unheard of for requests from Linux and Windows to take different routes from the same origin to the same destination?

NetHosted Customer Joined: 06 Dec 2011 Posts: 2

I've got it in the back of my mind that windows tracert uses ICMP echo packets, whereas linux traceroute uses UDP packets, by default. So yes, depending on the network configuartion between you and nethosted, it's possible that they'd take different routes.

you can switch linux traceroute to ICMP with the -I switch; do both windows and linux report the same (or similar) routes now?

Posted: Fri Dec 16, 2011 12:41 pm Post subject:

This is correct, Derek. Good catch.

We were having some issues with traceroute not running correctly with specific options but that is now cleared up and confirms that the ICMP/UDP thing is at the core of this particular issue.

I note there is also a -T option which uses TCP packets. This has yet another distinct behaviour. So I guess we have three methods of probing a route. Which one you use I suppose depends on what the problem is.

NetHosted Customer Joined: 06 Dec 2011 Posts: 2

Yep, it gets even "better" if you're using one of the BSDs, where there's a -P switch, allowing you select even more protocols.

Glad it helped

Client Support	Community	Server Status	Contact Us	Client Login
Email Hosting	Website Hosting	Reseller Hosting	VPS Hosting	Dedicated Servers