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Environment/Versions OSPF with dependent BFD Answer BFD does not start sending any messages until OSPF comes up first. Note that there is a bit in BFD messages that indicted as being Dependent or Independent type messages. It's been seen that even with one side as Dependent and the other side as Independent BFD still come up. Both sides recognize the BFD messages and brings up the sessions. This does not mean that some devices may prevent the sessions from coming up with mismatched types. If BFD and OSPF do not come up whether its Dependent mode or Independent mode: OSPF should be the first to be analyzed for any issues. Case 1: MTU size should match Case 2: Router Priority need to be other than zero if participating in DR election. Case 3: Database Description Master/Slave bit is determined by higher router ID. Make sure the lower router ID is able to become Slave Note that this is different from Designated Router indication. A DR can still be a Slave for Database Description behavior. In Dependent mode, BFD is not transmitted until OSPF comes up first.