I need to replace a 3660, which has 8 fastethernent and 4 serial. I have a 3640 and have found 2 4 port eithernet cards and a 4 port serial card would this work. This is only for a shourt fix. I been told a 3662 may be a better option if so would card can I use.
If you are referring to NM-4E and the NM-4T, then it should work fine on a 3640.
But with the NM-4E you are limited to 10Mbps per port