![]() – Algorithm to allow you to compute loop free paths over that database. ![]() “I need to know who I am connected too.” That the primary thing about hello. – Database (Distributive) allows everyone to see what the topology looks like. Spoke don’t have state Drother, A spoke and ospf flooding never occur downstream direction. So we can route downstream.īut how do spoke route upstream? Could be a simple static routes. Why would you ever us this, There is a case that you might use because if the hub doesn’t send state any LSA to all any downstream spoke can still learn information from the spoke. What we can do is go on hub and use “OSPF database all out” command. “There’s no rule in Hub&Spoke design, The spokes don’t necessarily state for all spokes” If we breakup the flooding domain using traditional ospf tools like “Areas/Hiding topology information thru summarization/prefix aggregation” One of the ways to make ospf to work in hub&spoke network or for any network where ospf is performing well would be the use of “Stop synchronizing the database” OSPF is design to have synchronize database “CAP Theorem” – Triangle based that is good for link state scalability. – Ring (If you know what you’re doing, be careful with “Micro Loop”) Hopefully vendors implement these new TLV based LSA formats quickly, as they will make OSPF much more extensible over the long run.Įp9 – What Your Mamma Never Told You About OSPFĬAP Theorem – Originally develop for databases. Once all the routers in the network (or, again, flooding domain) are advertising the new TLVs, then preference can be given to the new TLVs, and, finally, the old TLVs removed from the network. So long as there is any router flooding the older style TLVs within the netwrk (or flooding domain, there are options for both), the new TLVs will not be used to compute loop free paths. Migration between the old and new TLVs is managed much like migration between narrow and wide metrics in IS-IS routers capable of generating the new LSA types do so these new LSAs are marked so routers that do not understand them simply reflood them (they don’t process them in any way). The LSA provides the context, while the TLV provides the data. If a new address family needs to be supported, it is just a matter of creating a new TLV that can be used to describe this new reachability and putting it into the existing inter-area LSA. This allows the new inter area ruote LSA to carry new kinds of reachability information in the future by simply including new TLV types in the new LSA type. The individual fields are not TLVs the entire “old LSA” has been put into a TLV. OSPF TLVs: Taking advantage of improvements in computing power O Designed in a way which makes it easily extensible to any other layer 3 protocol suite. unrecognized LSA types are flooded to the neighbors making it more extensible that OSPFv2 ![]() O Exhibits implicit opaque LSA behaviour i.e. O The new RFCs (Traffic Engineering, GMPLS extensions, etc) written for OSPF now support TLV encoding. This in turn means that all the OSPF routers must be upgraded network-wide to make the new extensions work. O Since the unrecognized LSA types are not flooded to neighbors it makes it very difficult to extend OSPF. O LSAs of type 9, 10 and 11 have been introduced for advertising other application specific information and enough vendors now support this so that they are likely to get from one side of the network to the other. O It uses Link State Advertisements (LSAs) for advertising the routing information and the original specification called for dropping any unrecognized LSA type. We had to come out with OSPFv3 when we wanted to provide support for IPv6. O The downside of the above is that the packet formats are not at all extensible. This was primarily done because OSPF was meant to be an IPv4 only protocol. ![]() O Uses fixed format packets with all fields aligned at 32-bit boundaries for faster processing of the OSPF packets (doesn’t really matter anymore as the CPUs are really fast these days!).
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