IPad – Mac refuses to share internet connection over WiFi

The set-up that has worked for me for years and years on end suddenly – as of this morning – failed to work.

I have my Mac switched on most the time, and to connect to my iPad I set up a network for Wifi: Create Network > Channel 11 > Security 128-Bit WEP. On my iPad, I could select it, enter my password, and enjoy all the couch-based browsing I wanted. Nothing router or modem based, as far as I am aware.

It worked all fine and dandy until yesterday.

This morning it decided not to:

Wi-Fi has the self-assigned IP address 169.XXX.XXX.XXX and will not be able to connect to the Internet.

(As I found, the 169 here is a dummy IP address that indicates no connection can be made.)

Indeed, if I reconnect my iPad to this network, it warns that "This network is not connected to the Internet" (and "Join anyway" does, as expected, nothing).

I have:

• restarted my Mac
• restarted my iPad
• restarted my modem (although Internet works correctly through the Mac)
• created a new network
• created a new network location
• renewed the DCHP lease
• deleted files such as com.apple.network.identification.plist, NetworkInterfaces.plist, and preferences.plist, and some more, as per https://www.technobezz.com/fix-common-connection-wifi-issue-self-assigned-ip-macbook/ and similar pages
• copied the EtherNet IP address to Wi-Fi's TCP/IP, using "DHCP with Manual Address" as per https://discussions.apple.com/thread/5355232
• deleted the Keychain entry for the password, as per a YouTube movie that "works for some"
• created a new user (which might have solved it if it's due to local settings).

This seems to cover answers to similar issues such as in Wi-Fi no longer connecting to the internet and MacBook connects to network over Ethernet but not WiFi.

I must admit that I did not follow the suggestion "… or reinstall the OS" under the last one, as it does not sound too appealing. I run a pretty old OS: 10.7.5 – but not by choice. I have some software crucial for work that has been proven incompatible with newer versions of OS X.

I am not aware of any possible modem/router problems I might be having – if so, they appeared overnight. I've never had to configure anything else 'manually' before; default settings always worked.

ifconfig reports the following:

lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
    options=3<RXCSUM,TXCSUM>
    inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1 
    inet 127.0.0.1 netmask 0xff000000 
    inet6 ::1 prefixlen 128 
gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
stf0: flags=0<> mtu 1280
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
    options=27<RXCSUM,TXCSUM,VLAN_MTU,TSO4>
    ether 64:b9:e8:bb:06:9a 
    inet6 fe80::66b9:e8ff:febb:69a%en0 prefixlen 64 scopeid 0x4 
    inet 92.108.125.5 netmask 0xffffff00 broadcast 92.108.125.255
    media: autoselect (100baseTX <full-duplex>)
    status: active
en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
    ether 04:1e:64:f1:24:2d 
    inet6 fe80::61e:64ff:fef1:242d%en1 prefixlen 64 scopeid 0x5 
    inet 10.0.2.1 netmask 0xffffff00 broadcast 10.0.2.255
    inet 169.254.17.180 netmask 0xffff0000 broadcast 169.254.255.255
    media: autoselect
    status: active
fw0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 4078
    lladdr 64:b9:e8:ff:fe:bb:06:9a 
    media: autoselect <full-duplex>
    status: inactive
p2p0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> mtu 2304
    ether 06:1e:64:f1:24:2d 
    media: autoselect
    status: inactive
utun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1500
    inet 10.10.6.6 --> 10.10.6.5 netmask 0xffffffff 

but reading its man page only makes me realize how little I know of both the software and hardware parts of this (about this much -> ·). I do recognize 92.108.125.5 as my local IP address.

Anything left I can try? I'm slowly leaning towards the theory that although applying a sledgehammer might not fix it, at least it'll get rid of my frustration and give me an excuse to replace everything with new stuff.