Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
you have to take a closer look even at the routing on such a project. 100MBit requires extremly carefully routing (delay of the traces, capacitance, skew etc.) and i would not recommend OP's in such a project because there are some side effects that need a lot of debugging which is only effective if you are planning to do large series and want to spare some money there are some symmetrical digital transceivers from national which i would use. (hysteresis, delay etc.)
If you only wnat to extend a single line use a normal switch (not hub)! which might protect you from a lot of trouble! ;.)
Look any small Fast Ethernet switch chip (2 to 8 port), same of them
contains RAM and PHY, only most problem is Industrial temparature range ....
Redux AptaGate RS-120 have operating temparature from -40 to +85 C.
It need only add too PHY ( Intel LXT972A ) and SDRAM.