Am using open source OSPF software from ospf.org and running ospf daemon in host PC.

If router has interfaces in multiple area, then its an Area Border Router.

Is there a way to detect the router is ASBR in OSPF ?

Is the Network Planner explicitly tell the router would be an ASBR router,while configuring the network.

  • Whether Network Planner Will configure the router as ASBR explicitly or is there an way to detect automatically like ospf detects an ABR router. – user2857290 Oct 26 '16 at 8:53
  • An Area Border Router is actually an ABR. An ASBR is an Autonomous System Boundary Router and is the border between OSPF and another protocol. ASBRs produce Type 5 external LSAs through information redistributed from another protocol – Karl Billington Oct 26 '16 at 8:56
  • Hi Karl, While configuring OSPF, whether use should tell explicitly that the router is ASBR ? – user2857290 Oct 26 '16 at 9:00
  • If you use the redistribute command under the OSPF configuration it will become an ASBR – Karl Billington Oct 26 '16 at 9:04
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 13 '17 at 23:40

If you look at the type 1 Router LSA for an ABR or ASBR it will have the E flag set if it is an ASBR and the B flag set if it is an ABR

RFC 2328 A.4.2 page 206

bit E
    When set, the router is an AS boundary router (E is for

bit B
    When set, the router is an area border router (B is for border).

To configure an ASBR use the redistribute command within the OSPF configuration and the Router will become an ASBR


ASBR router means that your router or PC has interface in another routing domain/protocol apart from OSPF and you are advertising that network to OSPF domain.

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