OSPF: Difference between revisions
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;Route Selection Hierarchy - E1, E2, N1, N2 |
;Route Selection Hierarchy - E1, E2, N1, N2 |
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{{UC}} |
{{UC}} |
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= N1 N2 E1 E2 = |
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*Type 5 is E and Type 7 is N. |
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*An external route will be tagged as a Type 5 LSA (E route). |
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*This LSA is circulated throughout the OSPF domain except for Stub, Totally Stubby and NSSA. |
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*Stub areas are not allowed to have external routes there should be no ASBR in a Stub area, else configure it as NSSA. |
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*A route redistributed inside an NSSA area is a Type 7 LSA or N route. |
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*This LSA is circulated only within the NSSA area. |
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*E1 or E2 or N1 or N2 type routes are based upon cost of the route. |
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*E2 or N2 routes tell OSPF routers to set the metric as the metric at the point of redistribution.(At the ASBR) |
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*E1 or N1 routes tell OSPF routers to add the internal costs to reach the ASBR to the cost set at the point of redistrbution (At the ASBR) |
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1. N1 & E1 are preferred over N2 & E2 for the same route |
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2. When N1 & E1 have the same route to the destination, the one that have lower cost / Metric will win and get into the route table |
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3. If both N1 & E1 have the same cost, P-bit in N1 will be used to break the tide. |
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4. If P-bit is 0 (Then it would become E1) then we will have 2 E1 routes install into the routing table. (otherwise if maximum-path = 1, LSA with Higher Router-ID will get installed |
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= Withdraw OSPF Routes = |
= Withdraw OSPF Routes = |