i have an SRAM Red BB30 compact crankset....
i have an SRAM Red BB30 compact crankset. Is the ultegra 6700 cassette compatible?
Yes it will work fine. But if you are using SRAM derailleurs and chain you probably want to stick with the SRAM cassettes because it is is smoother. Another caveat, if you have more that one wheelset sticking with one brand of cassette makes wheel swaps easy, otherwise you will likely have to adjust the low and high stops when you change wheels.