perfSONAR User Q&A and Other Discussion

[Mark Feit <>]

Yiwen Huang writes:

 

I succeeded in publishing and performing measurements on local vmware hosts. But I still don't know why it failed  when executing the same commands on my cloud hosts (I've already turned the firewall off on both cloud hosts).

I have two cloud hosts and they both have public ip addresses, one ip address is 82.157.120.181 and the other is 49.232.21.90. 

On host "82.157.120.181", I executed the command:

# pscheduler task throughput --source 82.157.120.181 --dest 49.232.21.90

And I got a Failed result as shown below …

 

If your cloud provider is like most, public IPs are mapped to private ones on your instances using NAT.  Any attempt to bind to that address on a cloud host will fail because no interface is bound to it.

 

If you’re just going to be doing testing between cloud hosts, your best bet would be to set up a VPC among them and let each address the other directly by their private IPs.

 

There’s another trick you can do with DNS:   give the public addresses a FQDN (e.g., host1.example.net and host2.example.net) and insert an entry in each host’s /etc/hosts that overrides DNS and resolves those names to the private IP.   This doesn’t work for everything, though: the OWAMP protocol embeds local interfaces addresses in its messages and causes all sorts of problems if NAT is involved.

 

--Mark