FAQ

FAQ

1. How does FlowVisor slice ARP?

   The way the flowvisor handles arps is that it takes an arp request "who has $ip? tell $mac" and sends that to the slice that has flowspace for nw_dst=$ip.

2. Why does my controller get errors when it tries to flood an ARP?

   If your controller sends a flowmod without Layer 3 information, FV gives you an error, because if it installed that flowmod, the switch would match all ARPs. If your controller's flowmod includes L3 information, FV will pass along the flowmod as you expect. The NOX pyswitch controller, in particular, is known not to do this, and thus won't work with FlowVisor's ARP slicing.

3. When I start FV, I don't get any errors on the terminal, but it doesn't start up.

   Check /var/log/flowvisor/flowvisor-stderr.log, which is where FV logs startup errors (until it comes up enough to start using syslog).

4. Why am I getting a null pointer exception when I start FV?

   One possibility is if FV died badly, and left the database with a stale lock file. If you're 100% sure that FV isn't running, check in /usr/local/share/db; if you see a db.lck or dbex.lck file, you can safely remove this (but ONLY if FV is really NOT running).

5. Why am I getting a "java.lang.Error: Failed to create temporary file for jnidispatch library: java.i" error when I start FV?

   This can happen if /tmp/jna is owned by a user other than 'flowvisor' (typically root). If the directory is empty, it should be safe to remove it.

6. Can I run flowvisor as root or another user?

True through flowvisor 0.8.5 The flowvisor startup script (default: /etc/init.d/flowvisor) sets a variable FV_USER=flowvisor. The flowvisor program expects this user to exist AND be in the sudoers file. (default: /etc/sudoers)

As of 0.8.6 You may start FlowVisor as root (at your own risk) by setting the environment variable FV_RUN_AS_ROOT to 'yes'.

7. How do I backup my FlowVisor config and (re)load it? You can dump the flowvisor config at any time from a running config by running (this is the recommended approach):

   $ fvctl dumpConfig config.json.

   Alternatively, you can simply backup the internal database by copying it:

   $ cp <path_to_db>/FlowVisorDB <safe_backup_place>

   To reload flowvisor, you an either:

   $ fvconfig load config.json or copy the database back to its installed location.

8. I updated to 0.10 and I am getting a warning when FlowVisor starts up?

If the warning is of the form:

WARN: Table/View 'FSRQUEUE' already exists in Schema 'APP'.

Then this is normal, FlowVisor is updating the database structure to better serve you ;).