Multiple Interfaces to a Link Michael Barnes Cisco

Multiple Interfaces to a Link Michael Barnes Cisco Systems, Inc. 1

Multiple Interfaces to a Link ● ● Specified in RFC 2740 Too ambiguous 2

Multiple Interfaces to a Link ● ● ● Each of the multiple interfaces are assigned different Interface IDs, used to detect MIL. If an interface has multiple instance IDs, it will be grouped with other interfaces based on matching 3 instance Ids. Disable sending and receiving of OSPF packets on all but one of the interfaces to the link, except to receive self originated hellos Interface which continues to send and receive OSPF packets called the Active Interfaces which do not send and receive OSPF packets called Standby Interfaces 3

Multiple Interfaces to a Link ● ● ● All of the multiple interfaces to the link will however appear in the router-LSA Any link-local scope LSAs which are originated for a Standby Interface will be flooded over the Active Interface Prefixes on Standby Interfaces will be processed the same way as prefixes on the Active Interface If the Active Interface fails, another will have to take over, reforming all neighbor adjacencies from scratch All of the multiple interfaces to the link of adjacent router-LSAs must be found and used in the next-hop 4

Multiple Interfaces to a Link ● ● Standby state is added to the Interface finite state machine Events added to the Interface FSM – – Multiple. Interfaces. To. Link Active. Interface. Dead 5