Symptom

OSPF state could become BDR after old DR comes back. For example, When the Hu0/8/0/0 on R1 is shutdown state, R2 is OSPF DR for all subnets on the sub-interfaces Hun0/8/0/0.xxx 10.0.31.16/28 (Hu0/8/0/0.1203) R2 : DR 10.0.31.48/28 (Hu0/8/0/0.1204) R2 : DR 10.0.31.80/28 (Hu0/8/0/0.1205) R2 : DR After the Hu0/8/0/0 on R1 goes UP state, the Hu0/8/0/0.1203 and the Hu0/8/0/0.1205 on R1 are elected as DR while the Hu0/8/0/0.1204 are elected as BDR. 10.0.31.16/28 (Hu0/8/0/0.1203) R1 : DR <<< Not expected. R2 : BDR 10.0.31.48/28 (Hu0/8/0/0.1204) R1 : BDR R2 : DR 10.0.31.80/28 (Hu0/8/0/0.1205) R1 : DR <<< Not expected. R2 : BDR

Conditions

no shut main interface which has hundreds of sub-interfaces with OSPF neihbors in OSPF broadcast network.

Workaround

none

Further Problem Description