A network node (N1) for handling IGP flooding topology (FT) inconsistency by obtaining a new FT and setting a FT flag field (FT field) in a data packet (DP) to indicate whether a link between N1 and a second node (N2) is on the new FT. N1 transmits the DP to N2. N1 receives a second DP from N2 that includes the FT field set by N2 to indicate whether the link between the network node and N2 is on the new FT as determined by N2. N1 sets a FT inconsistency field in a link state packet to indicate an inconsistency in the new FT when the FT field set by N2 and the FT field set by N1 are different for a given time. N1 distributes the LS to at least one node in the network.