I have a 3750 and 6509 connected with fiber. When i take no shut on the interface at the 3750 side, the port goes in err-disable. I have tried a new fiber, new SFP and also changed ports. But the problem is still there. Below is the config and som output.
When I remove the "udld port" from the interface on the 3750, the port becomes up and traffic flows as normal.
Why?
3750:
interface GigabitEthernet1/0/25
switchport trunk encapsulation dot1q
switchport trunk native vlan 998
switchport trunk allowed vlan 1-179,190-679,682-689,800-4094
switchport mode trunk
udld port
Interface Gi1/0/25
---
Port enable administrative configuration setting: Enabled
Port enable operational state: Enabled
Current bidirectional state: Unidirectional
Current operational state: Disabled port
Message interval: 7
Time out interval: 5
No neighbor cache information stored
Sep 4 17:08:58: %UDLD-6-UDLD_PORT_RESET: UDLD reset interface Gi1/0/25
Sep 4 17:08:58: %PM-4-ERR_RECOVER: Attempting to recover from udld err-disable state on Gi1/0/25
Sep 4 17:09:01: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/25, changed state to up
Sep 4 17:09:02: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/25, changed state to up
Sep 4 17:09:05: %UDLD-4-UDLD_PORT_DISABLED: UDLD disabled interface Gi1/0/25, unidirectional link detected
Sep 4 17:09:05: %PM-4-ERR_DISABLE: udld error detected on Gi1/0/25, putting Gi1/0/25 in err-disable state
Sep 4 17:09:06: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/25, changed state to down
Sep 4 17:09:07: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/25, changed state to down
3750_sw#udld reset
1 ports shutdown by UDLD were reset.
3750_sw#sh udld gigabitEthernet 1/0/25
Interface Gi1/0/25
---
Port enable administrative configuration setting: Enabled
Port enable operational state: Enabled
Current bidirectional state: Neighbor's echo is empty
Current operational state: Detection
Message interval: 7
Time out interval: 5
Entry 1
---
Expiration time: 21
Device ID: 1
Current neighbor state: Neighbor's echo is empty
Device name: 015C738100
Port ID: Gi3/7
Neighbor echo empty
Message interval: 7
Time out interval: 5
CDP Device name: 6509_sw
3750_sw#sh udld gigabitEthernet 1/0/25
Interface Gi1/0/25
---
Port enable administrative configuration setting: Enabled
Port enable operational state: Enabled
Current bidirectional state: Neighbor's echo is empty
Current operational state: Detection
Message interval: 7
Time out interval: 5
Entry 1
---
Expiration time: 21
Device ID: 1
Current neighbor state: Unknown
Device name: 015C738100
Port ID: Gi3/7
Neighbor echo empty
Message interval: 7
Time out interval: 5
CDP Device name: 6509_sw
6500:
interface GigabitEthernet3/7
switchport
switchport trunk encapsulation dot1q
switchport trunk native vlan 998
switchport trunk allowed vlan 1-179,190-679,682-689,800-4094
switchport mode trunk
udld port
spanning-tree guard root
Interface Gi3/7
---
Port enable administrative configuration setting: Enabled
Port enable operational state: Enabled
Current bidirectional state: Unknown
Current operational state: Link down
Message interval: 7
Time out interval: 5
No neighbor cache information stored
Br
Geir
