Hello!
I can confirm that this particular line card (or any Nexus 9500 line card that utilizes the Cisco Cloud Scale ASIC - these PIDs tend to end in -EX, -FX, -FX2, -GX, etc.) does not support Fabric Extenders (FEXs). As far as I am aware, there are no plans to introduced support for FEXs on this family of Nexus 9500 line cards. My understanding is that this is due to the positioning of Nexus 9500 switches in the Nexus portfolio as spine switches in a leaf-spine (sometimes also called a Clos) network topology, typically configured with a protocol such as VXLAN BGP EVPN. Since spine switches are not intended to have hosts connected to them, they do not support FEXs, which are intended to have low-bandwidth hosts connected to them (such as iDRAC/iLO/CIMC connections, out-of-band management connections, smart PDU [Power Distribution Unit] management connections, etc.).
I'll also try to answer @russell.sage's question about why the N9K-X97160YC-EX line card would be marked as a replacement for the N9K-X9464PX line card, even though there's not direct feature parity between the two cards. In general, when a product is advertised as a replacement for another product in an End of Life announcement, that replacement advertisement is a suggestion that the replacement product most likely fulfills the majority of use cases the End of Life product previously fulfilled. There may be scenarios (such as this one with support for FEXs) where the previous product has a unique feature that is not supported by the replacement product. However, for the most part, the N9K-X97160YC-EX is similar to or better than the N9K-X9464PX line card:
- Both have the same quantity of ports with the same (or better) supported speeds. N9K-X9464PX offers 48x10G SFP+ ports with 4x40G QSFP ports, while N9K-X97160YC-EX offers 48x10/25G SFP28 ports with 4x40/100G QSFP28 ports.
- The N9K-X97160YC-EX has improved performance and buffering capabilities. N9K-X97160YC-EX supports 3.2 Tbps at 2.17 billion PPS and 80 megabytes of buffer, while N9K-X9464PX only supports 1.28 Tbps at 1.9 billion PPS and only 12 megabytes of buffer.
- The N9K-X97160YC-EX has drastically improved scalability over the N9K-X9464PX. For example, N9K-X97160YC-EX allows up to 1 million IPv4 Longest Prefix Match (LPM) routing table entries (unidimensional) and up to 1 million IPv4 host routing table entries (unidimensional), while the N9K-X9464PX only allows up to 128,000 and 104,000, respectfully.
I'll speak for a moment as a non-Cisco employee and simply as a network operator. As technology marches forwards, products age, and the "meta" of how networks are built changes (such as what topologies are currently in style, what protocols are in style, and so on) it becomes necessary for support for some older features to be dropped in new products. This allows vendors (and their developers) to focus time and energy on features that network operators are most likely to benefit from, allowing us to build modern networks that are stable and efficiently satisfy business needs. Sometimes, these features are dropped as part of the release of new products (such as FabricPath/OTV, which were supported in Nexus 5000 and 7000 products, but are not supported in Nexus 9000 products), and sometimes these features are dropped as part of generational updates (as is the case here, where FEXs on modular switches are not supported starting with the Cloud Scale generation of switches).
Now, that is not to say that Fabric Extender technology is completely obsolete and should be abandoned as soon as possible! In fact, some newer models of Nexus 9300s can be converted into a "Software FEX mode" and act as FEXs themselves, indicating that the technology is still alive for the foreseeable future. However, the positioning of modular Nexus 9500 switches in the network has changed such that it is considered unusual (or perhaps "off-meta" is a better term to use) for hosts to be connected directly to them, and so support for FEX technology doesn't necessary make sense under that new positioning.
I hope this helps - thank you!
-Christopher
