Setting MTU on lagg0 via Web UI deletes static IP on reboot in FreeNAS 11.0

[dmc]

FreeNAS 11.0-Release running on iXsystems FreeNAS Mini XL:

Creating a lagg0 with LACP from igb0 and igb1 and assigning a static IP address works OK using the web UI. Subsequently putting mtu 9216 in the lagg0 options field and rebooting brings up the system with no ethernet access. ifconfig shows an MTU of 9216 set in igb0, igb1, and lagg0, but no static IP address anywhere. Using ifconfig to give lagg0 an IP address and a netmask restores network functionality with the higher MTU. Another reboot, the IP address is lost again. Setting a lagg0 IP address with ifconfig to restore web access then clearing the options field for lagg0 and rebooting works fine, but the MTU is back at default. A not-so-brief look at the FreeNAS bootup logic led to creating rc.local in /conf/base/etc/ containing:
#!/bin/sh
ifconfig lagg0 192.168.2.16 netmask 255.255.255.0
which assigns the IP address at the end of the reboot. Yuck, but it works. My assumption is that the bootup logic that deals with an mtu in the interface options field is somehow scrambling the ifconfig syntax that assigns a static IP address to lagg0. It does manage to assign the mtu to all three interfaces, igb0, igb1, and lagg0, and the Web UI display of the lagg0 configuration has both IP address and options field correct.

This is not intended to provoke a discussion about jumbo frames themselves. The underlying FreeBSD is behaving exactly as it should - the problem lies with the scripts that configure the system at bootup from the Web UI database.

 

[m0nkey_]

Suggest you open a bug ticket at https://bugs.freenas.org

 

[dmc]

Done. Bug #24952.
Thank you,
dmc

 

[dmc]

And upon opening a bug I get the status changed this morning to Closed: Duplicate with no indication of what it might be a duplicate of, along with a blanket statement that MTUs should be set in the (invisible) member interfaces. Well, I've tried all that - see the bug report for more details - and besides, the MTUs are being correctly set in all interfaces. The problem is that the static IP address which is correct in the configuration database is not being correctly applied to the aggregate interface at startup when an MTU is present.

 

[dmc]

So if I have read my communications over a very noisy channel with the bug fixer correctly, a critical bugfix is going into the GUI code base to prevent directly setting the MTU of an aggregate device. Instead, the approved technique is to use the "Edit Members" button (which only appears when an interface is selected in the Link Aggregations page) to set the MTU of each member by putting, eg, "up mtu 9216" in the options field. Slightly more information is available in the discussion of Bug #24249, and indeed in the discussion of Bug #24952.

Other takeaways would be:
FreeNAS support can be very responsive when the issue is relevant to iXsystems commercial products.
Communicating with software engineers can be remarkably frustrating (but I already knew that)...