Network and Storage Protocols



It appears the default for the ip.fastpath.enable has changed in recent releases of ONTAP from off to on.

This has caused several odd errors on recent installations including filers refusing to join Active Directory and CIFS requests taking several minutes.

Has anyone got any recomendations as to when this option shoud be enabled or disabed?



With fastpath enabled, the filer will respond to the same MAC address and tries to send the packet back thru the same interface as it came in. This allows for loadbalancing on multiple trunk interfaces on the same subnet. Disabling this means that ONTAP has to look up its routing table to figure out where to stick the packet in and *might* introduce a delay. In other scenarios, if you have the filers connected to switches running HSRP, then it might conflict with the fastpath setting.

I would start by checking to see if there are any errors reported on the filer (netstat -nr, netdiag commands may be useful to check settings)

Another thing to check if you have multiple interfaces in the same subnet, then try disabling fastpath.

A few URLs to look into:


Thanks a lot for this posting!

It helped me solve a bunch of problems with a customer site (running some exotic switching infrastructure).

Problems we had with "options ip.fastpath.enable on":

- cifs setup (AD join) did not work reliably

- CIFS/SSH/HTTP access from Windows NLB (network load balancing) node did not work reliably

- probably other side effects we did not explicitly notice

All issues were gone by setting it to "off", no restart required.

Thanks again!


Hi, I have solved my problem about reading from NAS when I have disabled fastpath, but actually I have problems also writing in NAS. Any idea about it???


This resolved an issue we had with slow SSH logins to the filer.