uname -a outside the jail
sandbox.local 9.1-STABLE FreeBSD 9.1-STABLE #0 r+4298b38: Fri May 31 06:12:24 PDT 2013     root@build.ixsystems.com:/tank/build/nightlies/2013-05-31/os-base/amd64/tank/build/nightlies/2013-05-31/FreeBSD/src/sys/FREENAS.amd64  amd64

uname - a inside the jail
FreeBSD pj1 9.1-STABLE FreeBSD 9.1-STABLE #0 r+4298b38: Fri May 31 06:12:24 PDT 2013     root@build.ixsystems.com:/tank/build/nightlies/2013-05-31/os-base/amd64/tank/build/nightlies/2013-05-31/FreeBSD/src/sys/FREENAS.amd64  amd64


sandbox ~]$ ipfw list

outside the jail
--------------
00100 allow ip from any to any via lo0
00200 deny ip from any to 127.0.0.0/8
00300 deny ip from 127.0.0.0/8 to any
00400 deny ip from any to ::1
00500 deny ip from ::1 to any
00600 allow ipv6-icmp from :: to ff02::/16
00700 allow ipv6-icmp from fe80::/10 to fe80::/10
00800 allow ipv6-icmp from fe80::/10 to ff02::/16
00900 allow ipv6-icmp from any to any ip6 icmp6types 1
01000 allow ipv6-icmp from any to any ip6 icmp6types 2,135,136
02000 nat 100 ip from any to any
65000 allow ip from any to any
65535 allow ip from any to any

inside the jail
------------------
65535 allow ip from any to any

ifconfig

outside the jail
--------------
em0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=42098<VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,WOL_MAGIC,VLAN_HWTSO>
        ether 00:1a:a0:e3:2c:82
        inet 192.168.1.96 netmask 0xffffff00 broadcast 192.168.1.255
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
        media: Ethernet autoselect (1000baseT <full-duplex>)
        status: active
ipfw0: flags=8801<UP,SIMPLEX,MULTICAST> metric 0 mtu 65536
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384
        options=600003<RXCSUM,TXCSUM,RXCSUM_IPV6,TXCSUM_IPV6>
        inet6 ::1 prefixlen 128
        inet6 fe80::1%lo0 prefixlen 64 scopeid 0xa
        inet 127.0.0.1 netmask 0xff000000
        nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
bridge0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
        ether 02:6c:d1:cc:5f:00
        inet 192.168.99.1 netmask 0xffffff00 broadcast 192.168.99.255
        nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
        id 00:00:00:00:00:00 priority 32768 hellotime 2 fwddelay 15
        maxage 20 holdcnt 6 proto rstp maxaddr 2000 timeout 1200
        root id 00:00:00:00:00:00 priority 32768 ifcost 0 port 0
        member: epair1a flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
                ifmaxaddr 0 port 13 priority 128 path cost 2000
        member: epair0a flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
                ifmaxaddr 0 port 12 priority 128 path cost 2000
        member: em0 flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
                ifmaxaddr 0 port 1 priority 128 path cost 20000
epair0a: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=8<VLAN_MTU>
        ether 02:68:b5:00:0c:0a
        inet6 fe80::68:b5ff:fe00:c0a%epair0a prefixlen 64 scopeid 0xc
        inet 0.0.0.0 netmask 0xff000000 broadcast 255.255.255.255
        nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
        media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>)
        status: active
epair1a: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=8<VLAN_MTU>
        ether 02:80:b1:00:0d:0a
        inet6 fe80::80:b1ff:fe00:d0a%epair1a prefixlen 64 scopeid 0xd
        inet 0.0.0.0 netmask 0xff000000 broadcast 255.255.255.255
        nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
        media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>)
        status: active



inside the jail
------------------
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384
        options=600003<RXCSUM,TXCSUM,RXCSUM_IPV6,TXCSUM_IPV6>
        inet6 ::1 prefixlen 128
        inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
        inet 127.0.0.1 netmask 0xffffff00
        nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
epair0b: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=8<VLAN_MTU>
        ether 02:68:b5:00:0d:0b
        inet 192.168.99.27 netmask 0xffffff00 broadcast 192.168.99.255
        inet6 fe80::68:b5ff:fe00:d0b%epair0b prefixlen 64 scopeid 0x2
        nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
        media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>)
        status: active

/etc/resolv.conf inside the jail contents 
-------------------------------------------
# search local
nameserver 192.168.1.1
pass all

/etc/rc.conf inside the jail ( the loopback device would not start otherwise).
------------------------------
network_interfaces="lo0"
ifconfig_lo0="inet 127.0.0.1 netmask 255.255.255.0 up"  # default loopback device configuration and start