[c-nsp] 7600 SXF and IPv6

While the hardware capabilities are essentially the same, he is on a 7600, not a 6500. With SXF it didn't matter; with later it does, and he can't use SXI, but must derail that train to pick up the SRx train, which has different capabilities and issues.

To Anton, the OP, you need to look at the SXF and rebuilds release notes and see what they say; there are a lot of things to look at, and going SRx is going to change things for you; since I'm on Sup2 with SXF I can't go SRx with our 7600's anyway (chassis won't take Sup720 anyway; these are the OSR7609-branded (and epromed) clones of the 6509NEBS chassis that needs the special high speed fan upgrade that is so hard to find these days....).

And be sure to peruse the NANOG mailing list archives and read about the 6500-7600 split, especially the comments fom Gert.....