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= R&S Quick Notes =
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* The Neighbor IP used with OSPF distance command is the Neighbors Router-ID.
* “area range” summarize type 3 LSA’.
* “summary-address” summarize type 5 & 7 LSA’s.
* Auto-cost reference BW (Default = 100mb), formula = Ref-BW/Int-Bw.
* Switches do no support the interface command “ip ospf {pid} area {area-id}” .
* OSPF path selection: O > O*IA > O*E1 > O*E2.
* Using E1 metric type : Packets will be routed out the closest exit point of the network.
* Using E2 metric type : If you want packets to exit your network at the closest point to their external destination.
* Don’t forget with hub and spoke topology, “ip ospf priority 0″.
* PITFALL, when forbid to use RID, Loopbacks created later on might change the DR on you network after a reload.
* PITFALL, when forbid to use RID, Later requested to configure the same loopback on two routers, could break your adjacencies, as two router cant peer with the same RID.
* “no capability transit” – Mimics OSPFv1 behaviour for all data traffic to pass through Area-0.
* “max-metric” – Configures OSPF stub configurations
* “max-lsa” – Limit amount of non-local LSA’s
* “timers throttle lsa all” – Slow down update rate.
* “timers pacing lsa-group” – Group more LSA’s together in updates.
* “no ip ospf flood-reduction” – Disables every 30-min LSA DB refresh.
* “ip ospf database filter all out” – Breaks RFC, Stop sending LSA’s, but still receive LSA’s
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= Concept Recap =
*On a shared/ethernet network, only 2 router, DR & BDR will form full relationship, all others will stay in 2-way state.<ref>www.wipro.com</ref>
*If OSPF is stuck in ExStart State, MTU mismatch may be the cause, as it is requirement to successfully pass DBD Packets. Matching MTU is not a Adjacency Requirement, but is required to successfully pass Database Descriptor Packets
Matching MTU is not a Adjacency Requirement, but is required to successfully pass Database Descriptor Packets
*In OSPF, MTU Mismatch causes neighbors swinging between ExStart state to Down state
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