Um...how do you actually set values in MacTCP? I've tried poking at it some, but it's extremely different from modern network settings, and I can't seem to figure out how to actually get it to do anything sensible...
Configuring MacTCP for slirp networking in BasiliskII:
In MacTCP control panel, highlight the Ethernet icon
Then click "MORE..."
Obtain address "Manually"
Gateway Address: 10.0.2.2
Your IP address: 10.0.2.15
Set Subnet Mask with the slider to: 255.255.255.0
For the Domain name Server Information:
First row: A dot "." in the left field and 10.0.2.3 in the right field
Second row: Just a dot "." in the left field.
It should look like this:
(The dot in the second row is a workaround for a bug in MacTCP. You can enter more than one DNS address, but always use an extra row with just the dot.)
You can ignore other settings, the defaults will be OK.
Usually the Mac needs to be restarted after configuring MacTCP in order to make things work.