OSPF: Difference between revisions
→Withdraw OSPF Routes
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;Route Selection Hierarchy - E1, E2, N1, N2
{{UC}}
= N1 N2 E1 E2 =
*Type 5 is E and Type 7 is N.
*An external route will be tagged as a Type 5 LSA (E route).
*This LSA is circulated throughout the OSPF domain except for Stub, Totally Stubby and NSSA.
*Stub areas are not allowed to have external routes there should be no ASBR in a Stub area, else configure it as NSSA.
*A route redistributed inside an NSSA area is a Type 7 LSA or N route.
*This LSA is circulated only within the NSSA area.
*E1 or E2 or N1 or N2 type routes are based upon cost of the route.
*E2 or N2 routes tell OSPF routers to set the metric as the metric at the point of redistribution.(At the ASBR)
*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)
1. N1 & E1 are preferred over N2 & E2 for the same route
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
3. If both N1 & E1 have the same cost, P-bit in N1 will be used to break the tide.
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
= Withdraw OSPF Routes =
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