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5 - 240 WiNG 5 Access Point System Reference Guide
5.10.2.8 Overriding a Dynamic Routing (OSPF) Configuration
Overriding the Network Configuration
Open Shortest Path First (OSPF) is a link-state interior gateway protocol (IGP). OSPF routes IP packets within a single
routing domain (autonomous system), like an enterprise LAN. OSPF gathers link state information from neighbor
routers and constructs a network topology. The topology determines the routing table presented to the Internet Layer
which makes routing decisions based solely on the destination IP address found in IP packets.
OSPF detects changes in the topology, like a link failure, and plots a new loop-free routing structure. It computes the
shortest path for each route using a shortest path first algorithm. Link state data is maintained on each router and is
periodically updated on all OSPF member routers.
OSPF uses a route table managed by the link cost (external metrics) defined for each routing interface. The cost could
be the distance of a router (round-trip time), link throughput or link availability.
An OSPF network can be subdivided into routing areas to simplify administration and optimize traffic utilization. Areas
are logical groupings of hosts and networks, including routers having interfaces connected to an included network.
Each area maintains a separate link state database whose information may be summarized towards the rest of the
network by the connecting router. Areas are identified by 32-bit IDs, expressed either in decimal, or octet-based
dot-decimal notation. Areas can defined as:
• stub area - A stub area is an area which does not receive route advertisements external to the autonomous system
(AS) and routing from within the area is based entirely on a default route.
• totally-stub - A totally stubby area does not allow summary routes and external routes. that is, The only way for
traffic to get routed outside of the area is. A default route is the only way to route traffic outside of the area. When
there's only one route out of the area, fewer routing decisions are needed, lowering system resource utilization.
• non-stub - An area that imports autonomous system external routes and send them to other areas. However. it
still cannot receive external routes from other areas.
• nssa - NSSA is an extension of a stub that allows the injection of limited external routes into a stub area. If
selecting NSSA, no external routes, except a default route, enter the area.
• totally nssa - This an NSSA using 3 and 4 summary routes are not flooded into this type of area. It is also possible
to declare an area both totally stubby and not-so-stubby, which means that the area will receive only the default
route from area 0.0.0.0, but can also contain an autonomous system boundary router (ASBR) that accepts external
routing information and injects it into the local area, and from the local area into area 0.0.0.0
A router running OSPF sends hello packets to discover neighbors and elect a designated router. The hello packet
includes link state information and list of neighbors. OSPF is savvy with layer 2 topologies. If on a point-to-point link,
OSPF knows it is sufficient, and the link stays up. If on a broadcast link, the router waits for election before
determining if the link is functional.
To override a profile's dynamic routing configuration:
1. Select
Devices
2. Select a target device from the Device Browser in the lower, left-hand, side of the UI
3. Select
Profile Overrides
4. Select
Network
5. Select
OSPF.
from the Configuration tab.
from the Device menu to expand it into sub menu options.
to expand its sub menu options.
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