My Macbook is 'Starting Internet Recovery' But it can't connect to our WiFi in house.
I'm not an expert in Mac's, so can you tell me what you mean with the /sbin/ifconfig command ?
The easy option is to turn off MAC (Media Access Control) address checking in the router until after you get your Mac backup and running again. MAC address filtering is easily defeated anyway, so it is not very much protection.
If you still want to find your Mac's MAC address, then in Recovery Mode, you can go to the Menu bar and there should be an entry to start a Terminal session.
From the Terminal session started in Recovery Mode, enter the command
/sbin/ifconfig
Look for the 'en1:' entry. This should be the WiFi networking interface.
1 or 2 lines under the 'en1:' entry will be a line starting with 'ether' and followed by nn:nn:nn:nn:nn:nn
that will be the MAC address.
If there is no 'en1:' entry then try 'en0:'
At worse, you find ALL the 'ether' entries and add them ALL to your router.
The /sbin/ifconfig output should look similar to this (not exactly, but similar)
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
options=3<RXCSUM,TXCSUM>
inet6 ::1 prefixlen 128
inet 127.0.0.1 netmask 0xff000000
inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
nd6 options=1<PERFORMNUD>
gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
stf0: flags=0<> mtu 1280
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=10b<RXCSUM,TXCSUM,VLAN_HWTAGGING,AV>
ether 11:22:33:44:55:66
nd6 options=1<PERFORMNUD>
media: autoselect (none)
status: inactive
en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether 22:33:44:55:66:77 <<< Most likely WiFi MAC address location in the /sbin/ifconfig output
inet6 fe80::6aa8:6dff:fe2d:5cd4%en1 prefixlen 64 scopeid 0x5
inet 10.0.0.138 netmask 0xffffff00 broadcast 10.0.0.255
nd6 options=1<PERFORMNUD>
media: autoselect
status: active
fw0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 4078
lladdr a4:b1:97:ff:fe:8d:80:00
nd6 options=1<PERFORMNUD>
media: autoselect <full-duplex>
status: inactive
en2: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=60<TSO4,TSO6>
ether 33:44:55:66:77:88
nd6 options=1<PERFORMNUD>
media: autoselect <full-duplex>
status: inactive
bridge0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=63<RXCSUM,TXCSUM,TSO4,TSO6>
ether 44:55:66:77:88:99
Configuration:
id 0:0:0:0:0:0 priority 0 hellotime 0 fwddelay 0
maxage 0 holdcnt 0 proto stp maxaddr 100 timeout 1200
root id 0:0:0:0:0:0 priority 0 ifcost 0 port 0
ipfilter disabled flags 0x2
nd6 options=1<PERFORMNUD>
media: <unknown type>
status: inactive
p2p0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 2304
ether 55:66:77:88:99:aa
media: autoselect
status: inactive