Cisco IOS Static and Default Routes: AD, Floating, Null0
Working reference for static routing on Cisco IOS. The three forms (recursive next-hop, interface-only for point-to-point, fully-specified for multi-access), default routes (0.0.0.0/0), administrative distance values across sources (Connected 0, Static 1, eBGP 20, EIGRP 90, OSPF 110, IS-IS 115, RIP 120, EIGRP-external 170, iBGP 200, Unknown 255), floating static routes for backup paths (AD set higher than protocol), the permanent keyword and why you usually shouldn't use it, the Null0 trick for black-holing and for keeping summary advertisements alive in BGP, ODR for hub-and-spoke. Pitfalls: ARP pressure from recursive routes on Ethernet, floating AD set too low, wrong default-route gateway, longest-prefix-match surprises.