For others having issues with VM network routing...

virbr0 is usually installed by default on centos, etc. to facilitate containers networking via NAT.
If I'm not planning on running any containers I usually yum remove the associated packages,
and a reboot to make sure networking is OK.  

Sometimes the ipv4 autoconfig stuff also gets in the way of desired routing,
and I add NOZEROCONF=yes to /etc/sysconfig/network to disable it.

When I've seen the !X in traceroutes it has usually been a firewall config issue on the remote host I'm tracing to.



On Mon, Sep 14, 2020 at 11:50 AM Valerio Luccio <valerio.luccio@nyu.edu> wrote:

Thanks to all that gave me hints/suggestions, especially to Edward that pointed me to the right setup page.

I was able to set up correctly my internal switch network, but I'm still having issues with the virtual network that connects to the university backbone. The route on the VM is setup just like on the host and the engine. I also tested traceroute and found out something puzzling:

  1. traceroute on the host and the engine for any node on the university network returns the answer in milliseconds.
  2. traceroute on the VM for a node on my internal switch returns the answer in milliseconds with the flag.
  3. traceroute on the VM for the host or the engine returns answer after more than 10 seconds with the flag !X
  4. traceroute on the VM for other hosts on the network returns the flag !H (host not reachable).

According to the traceroute man pages the !X flag indicates "communication administratively prohibited". I temporarily turned off the firewall on the host and the engine and that removed the !X flag from 3, but did not speed it up and did not solve 4.

Anyone have any clue what I should try next ?

Thanks in advance,

--
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Valerio Luccio     (212) 998-8736
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