added prereqs

Author: marciocloudflare

src/content/docs/network-interconnect/express-cni/index.mdx

@@ -12,3 +12,18 @@ Connecting to Cloudflare directly with a Direct CNI reduces latency, makes your
 The use case for Direct CNI is Magic Transit or Magic WAN. If you have publicly routable origins that are behind Magic Transit over a Direct CNI, then all Cloudflare services that work with public origins will run over the CNI (for example, Load Balancer, WAF, Cache, etc).
 
 In the Cloudflare dashboard you can find Cloudflare's nearest Cloudflare data center, and order a Direct CNI connection with speeds up to 100 gigabits per second, as well as create a Letter of Authorization (LoA).
+
+## Prerequisites
+
+- Small Form-factor Pluggable (SFP) optics supported
+	- 10GBASE-LR optics will support up to 10 Km
+	- 100GBASE-LR4 optics will support up to 10 Km
+- Maximum MTU is 1500 bytes.
+
+### Limitations
+
+The following functionality is not yet supported on Direct CNI's dedicated ports.
+- Virtual LAN (VLAN) tagging (802.1Q)
+- Link Aggregation Control Protocol (LACP) and link aggregation. You can use ECMP instead.
+- Bidirectional Forwarding Detection (BFD)
+- IPv6 (you cannot create CNIs in an account with IPv6 beta enabled)