Crystals with slightly difference specs with the microcontroller?

Hi, i'm currently trying to build an ethernet interface for my project.

I'm using a National Semiconductor DP83847 ethernet transceiver. The
datasheet stated that it requires a 25Mhz 0.005% 50PPM oscillator.

My question is, lets say i can't find an exact match for the crystal,
such as:
1) Slightly lower/ higher frequency
2) Different accuracy, lets say 100PPM

What will be the effect for both cases?

 

It is almost certain that the initial accuracy 25MHz 0.005% is
necessary

The 50ppm is the drift - probably with temperature e.g. per 1degree C.
you might get away with 100 ppm if you are in a controlled temperature
environment.

Dan H