FreeNAS jails have a permanent arp entry for the default router

[data packrat]

I recently had to replace my home router after an old one failed, and found that my FreeNAS jails could no longer access the Internet. I traced this to the arp tables in my jails having a permanent arp table entry for the default router, which had the MAC address of the old router. The host O/S did not mark it's default router entry as permanent, and so worked after the router replacement. A restart of the jail picked up the new router MAC address, again marking it as a permanent arp table entry (The only other permanent arp entry is for the jail's own IP address).

Is this a bug ? - or is there some good reason for this, perhaps to make things work in the bridged ethernet configuration that the jails use.

Thanks.

 

[SweetAndLow]

After a reboot it got updated? Doesn't seem that permanent to me. I wonder what what timeout is set to.

Sent from my Nexus 5X using Tapatalk

 

[data packrat]

After a reboot it got updated? Doesn't seem that permanent to me. I wonder what what timeout is set to.

Sent from my Nexus 5X using Tapatalk

"sysctl net.link.ether.inet.max_age" shows that FreeNAS is using a 1200 second = 20 minute timeout.
"cat /proc/sys/net/ipv4/neigh/default/gc_stale_time" on a nearby Ununtu Linux box shows 60 seconds.
A "permanent" entry lasts until someone changes it, or the system goes down.
ARP values are normally supposed to timeout to allow for changes, setting a permanent entry is for special cases (such as your own address) and prevents the entry being updated... My new router announced itself with a "gratuitous arp" broadcast. This correctly updated the main FreeNAS box, but the permanent entry in the jail caused it to block the update, and log messages like "arp: 00:1d:55:f9:b4:00 attempts to modify permanent entry for 192.168.1.1 on epair4b".

 

[Kam]

I have the same behaviour on my 9.10.1-U4.

on freenas host:
[root@freenas] ~# arp 192.168.1.1
router.asus.com (192.168.1.1) at ........ on bge0 expires in 1193 seconds [ethernet]

and in jail:
[root@freenas] ~# jexec wordpress arp 192.168.1.1
router.asus.com (192.168.1.1) at ........ on epair2b permanent [ethernet]

MAC adresses of router seen from host and jail were same, I have deleted it here.
So jail is adding default router address as permanent, even if host does not.