54The output indicates that the link status of both GigabitEthernet 1/0/49 and GigabitEthernet 1/0/50 isdown.Assume that in this example, the unidirectional links are caused by cross-connected fibers. Correct thefiber connections, and then bring up the ports shut down earlier.# On Device A, bring up GigabitEthernet 1/0/49 and GigabitEthernet 1/0/50:[DeviceA-GigabitEthernet1/0/50] undo shutdown[DeviceA-GigabitEthernet1/0/50]%Jan 18 18:22:11:698 2010 DeviceA IFNET/3/LINK_UPDOWN: GigabitEthernet1/0/50 link statusis UP.[DeviceA-GigabitEthernet1/0/50] quit[DeviceA] interface gigabitethernet 1/0/49[DeviceA-GigabitEthernet1/0/49] undo shutdown[DeviceA-GigabitEthernet1/0/49]%Jan 18 18:22:46:065 2010 DeviceA IFNET/3/LINK_UPDOWN: GigabitEthernet1/0/49 link statusis UP.The output indicates that the link status of both GigabitEthernet 1/0/49 and GigabitEthernet 1/0/50 isnow up.Troubleshooting DLDPSymptomTwo DLDP-enabled devices, Device A and Device B, are connected through two fiber pairs, in which twofibers are cross-connected. The unidirectional links cannot be detected; all the four ports involved are inAdvertisement state.AnalysisThe problem can be caused by the following.• The intervals to send Advertisement packets on Device A and Device B are not the same.• DLDP authentication modes/passwords on Device A and Device B are not the same.SolutionMake sure the interval to send Advertisement packets, the authentication mode, and the passwordconfigured on Device A and Device B are the same.
