Well, any frame-relay CPE router cannot create FECN's or BECN's. Routers are not supposed to. Only frame-relay switches are supposed to send FECN's and BECN's. Although Cisco routers can be configured to 'reflect' FECN's into BECN's, they cannot independently generate FECNs/BECNs themselves. Ask yourself - how exactly would a router know about congestion within the frame-relay cloud?
Now, if you're talking about Cisco routers acting as frame-relay switches, then they can indeed mark the FECN/BECN bit. But that's probably not what you mean.
