> 2. Does SIP (SPA Interface Processors) for 7600 works in 6500 > too? Yes. The 7600 *is* a 6500 (and vice versa). > Within 7600 series, is SIP/SPA available for 7604 only or all > 7600 series? Chassis of all sizes. > what about supervior requirements, is SUP720 only? Yes, at least currently SIPs/SPAs are only supported with Sup720. -A