OSPF calculates separate routes for each Type of Service (TOS). Calculates new loop-free routes after a period of convergence. Host routes are considered to be subnets whose masks are “all ones” (0xffffffff). All OSPF protocol exchanges are authenticated. Two different subnets of the same IP network number may have different sizes (i.e., different masks). 1.2. Definitions of commonly used terms This section provides definitions for terms that have a specific meaning to the OSPF protocol and that are used throughout the text. OSPF also provides for the authentication of routing updates, and utilizes IP multicast when sending/receiving the updates. The OSPF protocol is based on link-state or SPF technology. 1.3. Brief history of link-state routing technology OSPF is a link state routing protocol. Link State ID of 10.0.0.255. Security Considerations All OSPF protocol exchanges are authenticated. If one or more of the routers have declared themselves Designated Router (i.e., they are currently listing themselves as Designated Router in their Hello Packets) the one having highest Router Priority is declared to be Designated Router. The author would like to thank Fred Baker, Jeffrey Burgan, Rob Coltun, Dino Farinacci, Vince Fuller, Phanindra Jujjavarapu, Milo Medin, Kannan Varadhan and the rest of the OSPF working group for the ideas and support they have given to this project. Content has been created by GSA Conte nt G ener at or DEMO.
It has been designed expressly for the TCP/IP internet environment, including explicit support for IP subnetting, TOS-based routing and the tagging of externally-derived routing information. We want all internet traffice to be routed to a specific network. IP packets are routed “as is” — they are not encapsulated in any further protocol headers as they transit the Autonomous System. A packet is routed to the best (i.e., longest or most specific) match. First, an Hello Packet may be received from a neighbor claiming to be itself the Backup Designated Router. This means that any two eligible routers are always exchanging Hello Packets, which is necessary for the correct operation of the Designated Router election algorithm. Contained in the neighbor’s Hello packets, this item is used when selecting the Designated Router for the attached network. The Backup Designated Router is identified here by its IP interface address on the network. If the subnet mask associated
with the interface via SNMP or ICMP does not match the
subnet’s mask in NNM, then an Inconsistent Subnet Mask event
is generated by netmon. The subnet mask chosen by NNM for a newly discovered
node or interface is based on the subnet mask discovered
by NNM for each subnet, instead of forcing the same sub-
net mask for an entire IP network. Data has been c reated with G SA C ontent Generat or DEMO!
All routers run the exact same algorithm, in parallel. Both HelloInterval and RouterDeadInterval must be the same for all routers attached to a common network. However, the AS boundary router’s routing table entry must indicate a set of paths which utilize a single area. From the topological database, each router constructs a tree of shortest paths with itself as root. 216 1. Introduction This document is a specification of the Open Shortest Path First (OSPF) TCP/IP internet routing protocol. This is a departure from the Bellman-Ford base used by traditional TCP/IP internet routing protocols. Finally, the algorithm has been modified for efficient operation in TCP/IP internets. Note: findroute and the associated Locate Route operation
are NNM only functions. As such, it has all of the parameters associated with a router interface (see Section C.3). It quickly detects topological changes in the AS (such as router interface failures). In this state, the lower-level protocols have indicated that the interface is unusable. We have 2 x 7030 controlllers that we want to change the default route on. Each route distributed by OSPF has a destination and mask. OSPF enables the flexible configuration of IP subnets.
Network addresses are assigned by a global
administrative body to particular organizations, while the
partitioning into subnets is left to the individual organi-
zations. Each individual piece of this database is a particular router’s local state (e.g., the router’s usable interfaces and reachable neighbors). Each participating router has an identical database. 208 E.3 Obsoleting LSInfinity in router links advertisements . However, when one-directional links (i.e., cost of LSInfinity in one direction, but not the other) are possible, some routers may detect the existence of virtual links while others may not. For example, if an area uses a simple password scheme for authentication, a separate password may be configured for each network contained in the area. Separate Autonomous Systems may be running different IGPs. Router ID A 32-bit number assigned to each router running the OSPF protocol. Suppose in our example both Router RT5. The router distributes its local state throughout the Autonomous System by flooding. At this point the adjacency is listed in link state advertisements.