Hello, I have attached an image of a network I am working on.
I have enabled OSPF on all five routers.
I notice that only the link (circled in pink) between 'xyzCompany' and 'Admin' routers has elected a DR (xyzCompany) and a BDR (Admin).
This link between the two is classified as a "BROADCAST" link rather than a "POINT TO POINT" link.
I am still learning about OSPF. Can someone please tell me why it is only the link between these two routers that is configured with a DR and a BDR and the broadcast classification, while the other router links dont have a DR/BDR and are classified as point to point links ?
Thanks for any explanation
It is a bit difficult to be sure but it looks in the drawing like the other links are serial point to point links. Can you confirm that this is the case?
OSPF makes a distinction about network types. For networks like Ethernet where there potentially could be multiple neighbors on an interface OSPF uses the concept of DR and BDR. After election of DR and BDR then all OSPF routers on the segment form adjacency with the DR and with the BDR (but not with other neighbors on the segment).
On serial point to point links (PPP, HDLC, Frame Relay point to point subinterface, etc) OSPF knows that there can not be more than one neighbor on the segment. Therefore there is no need to the mechanism of DR and BDR and so the OSPF routers immediately form adjacency with each other.