UDLD Configuration
- Tracy Yang
Owned by Tracy Yang
Nov 13, 2023
4 min read
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UDLD (Unidirectional Link Detection) using for detecting optical fiber unidirectional link. It supports two modes of operation: normal mode(the default) and aggressive mode. In normal mode, UDLD can detect unidirectional links due to mis-connected interfaces. In aggressive mode, UDLD can also detect unidirectional links due to one-way traffic, twisted-pair links, and mis-connected interfaces. You can enable UDLD globally or on specific ports. When UDLD detectes uni-directional fault, the port status will be setted Disabled(UDLD) and down, and there is no udld neighbor. In addition, UDLD can detect the self loop port and disable this port. Self loop means TX links to RX on the same port.
Caution:
- For the case of TX-RX (RX indicates the receiving end, and TX indicates the sending end) self-loops on one ethernet port, the port status will be set to Disabled (UDLD) and down, and there will be no UDLD neighbor.
- Do not configure up-mode with UDLD, as this may cause the peer interface to be disabled unexpectedly by UDLD.
Configure UDLD normal mode on global
admin@XorPlus# set protocols udld disable false admin@XorPlus# commit Commit OK. Save done.
Configure UDLD aggressive mode on global
admin@XorPlus# set protocols udld disable false admin@XorPlus# set protocols udld aggressive true admin@XorPlus# commit Commit OK. Save done.
Configure UDLD normal mode on Specific Port
admin@XorPlus# set protocols udld interface te-1/1/27 disable false admin@XorPlus# commit Commit OK. Save done.
Configure UDLD aggressive mode on Specific Port
admin@XorPlus# set protocols udld interface te-1/1/27 disable false admin@XorPlus# set protocols udld interface te-1/1/27 aggressive true admin@XorPlus# commit Merging the configuration. Commit OK. Save done.
Configure UDLD Message-interval
admin@XorPlus# set protocols udld message-interval 20 admin@XorPlus# commit Commit OK. Save done.
UDLD status as follows when the link is good
admin@Xorplus# run show udld neighbors
Port Device Name Device ID Port ID state
-------- ----------- ----------- ------------ ---------------
te-1/1/27 3295 QTFQXI10700003 te-1/1/49 bi-directional
admin@Xorplus# run show udld interface te-1/1/27
Interface te-1/1/27
----------------------------------------
Udld enabled, aggressive mode
Current bidirectional state: bi-directional
Current phase: advertisement
Message interval: 15s
Timeout interval: 5s
neighbor 1
------------------
Expiration time: 43.58s
Device ID: QTFQXI10700003
Port ID: te-1/1/49
Message interval: 20s
Timeout interval: 5s
Device name: 3295
UDLD status as follows when UDLD detect uni-directional fault
admin@Xorplus# run show udld neighbors Port Device Name Device ID Port ID state -------- ----------- ----------- ------------ --------------- admin@Xorplus# run show udld interface te-1/1/27 Interface te-1/1/27 ---------------------------------------- Udld enabled Current bidirectional state: uni-directional Current phase: linkdown Message interval: 7s Timeout interval: 5s admin@XorPlus# run show interface gigabit-ethernet te-1/1/27 Physical interface: te-1/1/27, Enabled, error-discard True(UDLD), Physical link is Down Interface index: 27, SFP type: SR/850 Description: Link-level type: Ethernet, MTU: 1514, Speed: Auto, Duplex: Full Source filtering: Disabled, Flow control: Disabled, Auto-negotiation: Enabled Interface flags: Hardware-Down SNMP-Traps Internal: 0x0 Interface rate limit ingress:unlimited, egress:unlimited Interface burst limit ingress:unlimited, egress:unlimited Current address: 00:90:4c:06:a5:73, Hardware address: 00:90:4c:06:a5:73 Traffic statistics: 5 sec input rate 0 bits/sec, 0 packets/sec 5 sec output rate 0 bits/sec, 0 packets/sec Input Packets............................16 Output Packets...........................1360 Input Octets.............................1797 Output Octets............................157178
UDLD status when self loop link
The example is that tx connect with rx on the same port te-1/1/27. The udld status will be transmit-to-receive loop, and the port status will be setted Disabled(UDLD) and down, and there is no udld neighbor.
admin@Xorplus# run show udld neighbors Port Device Name Device ID Port ID state -------- ----------- ----------- ------------ --------------- admin@Xorplus# run show udld interface te-1/1/27 Interface te-1/1/27 ---------------------------------------- Udld enabled, aggressive mode Current bidirectional state: transmit-to-receive loop Current phase: linkdown Message interval: 7s Timeout interval: 5s admin@XorPlus# run show interface gigabit-ethernet te-1/1/27 Physical interface: te-1/1/27, Disabled(UDLD), error-discard False, Physical link is Down Interface index: 27, SFP type: SR/850 Description: Link-level type: Ethernet, MTU: 1514, Speed: Auto, Duplex: Full Source filtering: Disabled, Flow control: Disabled, Auto-negotiation: Enabled Interface flags: Hardware-Down SNMP-Traps Internal: 0x0 Interface rate limit ingress:unlimited, egress:unlimited Interface burst limit ingress:unlimited, egress:unlimited Precision Time Protocol mode:none Current address: 00:90:4c:06:a5:73, Hardware address: 00:90:4c:06:a5:73 Traffic statistics: 5 sec input rate 0 bits/sec, 0 packets/sec 5 sec output rate 0 bits/sec, 0 packets/sec Input Packets............................16 Output Packets...........................1360 Input Octets.............................1797 Output Octets............................157178
Recover port status Disabled(UDLD)
You can through down, up the port to recover the status Disabled(UDLD)
admin@XorPlus# set interface gigabit-ethernet te-1/1/27 disable true admin@XorPlus# commit Commit OK. Save done. admin@XorPlus# set interface gigabit-ethernet te-1/1/27 disable false admin@XorPlus# commit Commit OK. Save done. admin@XorPlus# run show interface gigabit-ethernet te-1/1/27 Physical interface: te-1/1/27, Enabled, error-discard False, Physical link is Up Interface index: 27, SFP type: SR/850 Description: Link-level type: Ethernet, MTU: 1514, Speed: Auto, Duplex: Full Source filtering: Disabled, Flow control: Disabled, Auto-negotiation: Enabled Interface flags: Hardware-Down SNMP-Traps Internal: 0x0 Interface rate limit ingress:unlimited, egress:unlimited Interface burst limit ingress:unlimited, egress:unlimited Precision Time Protocol mode:none Current address: 00:90:4c:06:a5:73, Hardware address: 00:90:4c:06:a5:73 Traffic statistics: 5 sec input rate 0 bits/sec, 0 packets/sec 5 sec output rate 0 bits/sec, 0 packets/sec Input Packets............................16 Output Packets...........................1360 Input Octets.............................1797 Output Octets............................157178
Or you can using follow command to recover the status Disabled(UDLD)
admin@XorPlus# run clear udld admin@XorPlus# run show interface gigabit-ethernet te-1/1/27 Physical interface: te-1/1/27, Enabled, error-discard False, Physical link is Up Interface index: 27, SFP type: SR/850 Port mode: access Description: Link-level type: Ethernet, MTU: 1514, Speed: Auto, Duplex: Full Source filtering: Disabled, Flow control: Disabled, Auto-negotiation: Enabled Interface flags: Hardware-Down SNMP-Traps Internal: 0x0 Interface rate limit ingress:unlimited, egress:unlimited Interface burst limit ingress:unlimited, egress:unlimited Precision Time Protocol mode:none Current address: 00:90:4c:06:a5:73, Hardware address: 00:90:4c:06:a5:73 Traffic statistics: 5 sec input rate 0 bits/sec, 0 packets/sec 5 sec output rate 0 bits/sec, 0 packets/sec Input Packets............................16 Output Packets...........................1360 Input Octets.............................1797 Output Octets............................157178
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