Network unreachable in jail, dns resolution works fine

Hi everyone,

I'm not a FreeBSD / Linux pro but hope, you guys can help me resolve an issue I'm having with jails being unable to connect to the Internet.

I've been running my FreeNAS system for a while, having upgraded from FreeBSD 9.x via 10.x to 11.x. I've got a couple of jails (all from the FreeBSD 9 times) which work fine. Today, I created a new jail, based off the official 11.0 standard template here.

When I try to ping a host on the Internet, I do get a network unreachable error.

Here is some more information:

root@experimental:/ # host has address has IPv6 address 2a00:1450:4001:81d::200e mail is handled by 20 mail is handled by 50 mail is handled by 30 mail is handled by 40 mail is handled by 10

root@experimental:/ # ping
PING ( 56 data bytes
ping: sendto: Network is unreachable

root@experimental:/ # traceroute
traceroute: findsaddr: failed to connect to peer for src addr selection.

root@experimental:/ # netstat -rn
Routing tables
(0) (0) U
(0) (0) UG
(0) (0) UH  13473
(0) (0) U
(0) (0) UHS  13473
(0) (0) U  13473
(0) (0) UHS  13473
(0) (0) U
(0) (0) UHS  13473

root@experimental:/ # ifconfig
lo0: flags=8048<LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384
    inet netmask 0xff000000
epair2b: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
    ether 4e:61:35:52:5b:18
    inet netmask 0xffffff00 broadcast
I noticed, that in the older jails, ifconfig reported "status: active" for the epair$b interface, while in the newly created one, there is no "status: active". Does that maybe point to the problem?
The 'problem' is that FreeNAS is a highly customized FreeBSD derivative. Solutions that work for FreeBSD may not work or be correct for FreeNAS.