I set up a Classic with an Asante SCSI Ethenet Adapter. I had no issues with my intranet (which you seem to be having) but had major issues getting from the Classic to the Internet. Mactcp doesn't respond properly to QOS packets. Here is a posting I made to Applefritter:

I finally made a big step forward with my mac classic. The bottom line is to co-exist with modern ISPs, mactcp needs to be updated. I ran into a number of issues I thought I should share.

1. mactcp 2.06 needs to be patched to become mactcp 2.1. Just search the web for mactcp 2.1 and you will find the patch.

2. You need a clean copy of mactcp 2.06 to use the patch.

3. The patch may fail with error code 50 right near the end. Not sure why but it seems to be a non-issue.

4. Ignore some university websites that say you need a 68030 Mac or system 7.x. The patch works with my classic running 6.07.

5. If you want to keep your orginal mactcp file move it out of the system folder. I made the mistake of keeping a "copy of mactcp" in my system folder. Since "c" comes before "m", the system was loading the older non-patched version of mactcp.

So far I can use fetch, eudora, and internews with the patch.

Mike