What is the default OSPF interface priority on all interfaces?

The default OSPF interface priority on all interfaces is 1. This value determines the likelihood of an interface becoming the designated router (DR) in a multi-access network segment. OSPF uses this priority value during the election process for DR and backup designated router (BDR). By default, all interfaces are assigned a priority of 1, meaning that all interfaces have an equal chance of becoming the DR and BDR unless configured otherwise.

When multiple interfaces are present on a network segment, if the priority values were all set to 1, OSPF would fall back to using the router IDs to decide the DR. A higher priority number increases the chances that an interface will be elected as DR, while a priority of 0 would prevent an interface from becoming DR altogether. This understanding is fundamental when configuring OSPF to ensure optimal routing performance in a network.