network cisco ccna gns3 certification arteq

network cisco ccna gns3 certification arteq
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Sunday, August 12, 2012

link state packets from the Pleistocene epoch...

check out these graphics... made with an etch a sketch...

Link-State Packets

There are different types of Link State Packets, those are what you normally see in an OSPF database (Appendix A). The different types are illustrated in the following diagram:
As indicated above, the router links are an indication of the state of the interfaces on a router belonging to a certain area. Each router will generate a router link for all of its interfaces. Summary links are generated by ABRs; this is how network reachability information is disseminated between areas. Normally, all information is injected into the backbone (area 0) and in turn the backbone will pass it on to other areas. ABRs also have the task of propagating the reachability of the ASBR. This is how routers know how to get to external routes in other ASs.
Network Links are generated by a Designated Router (DR) on a segment (DRs will be discussed later). This information is an indication of all routers connected to a particular multi-access segment such as Ethernet, Token Ring and FDDI (NBMA also).
External Links are an indication of networks outside of the AS. These networks are injected into OSPF via redistribution. The ASBR has the task of injecting these routes into an autonomous system.


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