Suudenly port channel went down ( No operational members )

[mradul1811]

2020 Feb 16 19:31:25  %ETH_PORT_CHANNEL-5-FOP_CHANGED: port-channel21: first operational port changed from Ethernet1/20 to none
2020 Feb 16 19:31:25  %ETH_PORT_CHANNEL-5-PORT_DOWN: port-channel21: Ethernet1/20 is down
2020 Feb 16 19:31:25  %ETHPORT-5-IF_DOWN_LINK_FAILURE: Interface Ethernet1/20 is down (Link failure)

# show interface po21
port-channel21 is down (No operational members)
vPC Status: Down, vPC number: 21 [packets forwarded via vPC peer-link]
Hardware: Port-Channel, address: 0000.0000.0000 (bia 0000.0000.0000)
Description: SCRBHPVDKRUP002-PO
MTU 1500 bytes, BW 100000 Kbit, DLY 10 usec
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA
Port mode is trunk
auto-duplex, 10 Gb/s
Input flow-control is off, output flow-control is off
Switchport monitor is off
EtherType is 0x8100
Members in this channel: Eth1/20

[balaji.bandi]

DUPLICATE

[balaji.bandi]

Since we do not have visibility and physical connection diagram, as per the information.

This more of Link issue with cable associated with interface "Ethernet1/20", investigate the physical issue.

is the device is dual-homed? post output below from both the switches

show vpc 21

show interface eth 1/20

[mradul1811]

Sw2# show vpc 21

vPC status
----------------------------------------------------------------------------
id Port Status Consistency Reason Active vlans
------ ----------- ------ ----------- -------------------------- -----------
21 Po21 down* success success -

Sw2# show interface eth 1/20
Ethernet1/20 is down (Link not connected)
Dedicated Interface
Belongs to Po21
Hardware: 1000/10000 Ethernet, address: 547f.ee4a.b29b (bia 547f.ee4a.b29b)
Description: SCRBHPVDKRUP002-Net
MTU 1500 bytes, BW 10000000 Kbit, DLY 10 usec
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA
Port mode is trunk
auto-duplex, 10 Gb/s, media type is 10G
Beacon is turned off
Input flow-control is off, output flow-control is off
Rate mode is dedicated
Switchport monitor is off
EtherType is 0x8100
Last link flapped 13:33:15
Last clearing of "show interface" counters never
100 interface resets
30 seconds input rate 0 bits/sec, 0 packets/sec
30 seconds output rate 0 bits/sec, 0 packets/sec
Load-Interval #2: 5 minute (300 seconds)
input rate 0 bps, 0 pps; output rate 0 bps, 0 pps
RX
75016380566 unicast packets 15773829 multicast packets 14244939 broadcast packets
75046399334 input packets 73686682644004 bytes
30357528802 jumbo packets 0 storm suppression bytes
0 runts 0 giants 0 CRC 0 no buffer
0 input error 0 short frame 0 overrun 0 underrun 0 ignored
0 watchdog 0 bad etype drop 0 bad proto drop 0 if down drop
0 input with dribble 0 input discard
0 Rx pause
TX
73758935113 unicast packets 2260820346 multicast packets 578059784 broadcast packets
76597815243 output packets 71295483225726 bytes
32879617712 jumbo packets
0 output error 0 collision 0 deferred 0 late collision
0 lost carrier 0 no carrier 0 babble 0 output discard
0 Tx pause

============

Sw1# show vpc 21

vPC status
----------------------------------------------------------------------------
id Port Status Consistency Reason Active vlans
------ ----------- ------ ----------- -------------------------- -----------
21 Po21 up success success 274-278,300
,323-327,33
1

Sw1# show interface eth1/20
Ethernet1/20 is down (Link not connected)
Dedicated Interface
Hardware: 1000/10000 Ethernet, address: 547f.eefb.97fb (bia 547f.eefb.97fb)
Description: SCRBHPVDKRUP002-ISCSI
MTU 1500 bytes, BW 10000000 Kbit, DLY 10 usec
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA
Port mode is access
auto-duplex, 10 Gb/s, media type is 10G
Beacon is turned off
Input flow-control is off, output flow-control is off
Rate mode is dedicated
Switchport monitor is off
EtherType is 0x8100
Last link flapped 13:40:28
Last clearing of "show interface" counters never
63 interface resets
30 seconds input rate 0 bits/sec, 0 packets/sec
30 seconds output rate 0 bits/sec, 0 packets/sec
Load-Interval #2: 5 minute (300 seconds)
input rate 0 bps, 0 pps; output rate 0 bps, 0 pps
RX
52004421058 unicast packets 10303886 multicast packets 17951726 broadcast packets
52032676670 input packets 61192880704897 bytes
0 jumbo packets 0 storm suppression bytes
0 runts 0 giants 0 CRC 0 no buffer
0 input error 0 short frame 0 overrun 0 underrun 0 ignored
0 watchdog 0 bad etype drop 0 bad proto drop 0 if down drop
0 input with dribble 0 input discard
0 Rx pause
TX
59568304179 unicast packets 347125700 multicast packets 306717924 broadcast packets
60222147803 output packets 81135862590974 bytes
21 jumbo packets
0 output error 0 collision 0 deferred 0 late collision
0 lost carrier 0 no carrier 0 babble 0 output discard
0 Tx pause

[balaji.bandi]

As per your output both the side interface down, but the surprise was one of the switches vPC 21 is shows as a success.,

what is the device connected to this vPC 21. how many interfaces participated on the port-channel 

can you post below configuration also from both the switches?

show run interface port-chan 21

show run interface eth 1/20

[Martin L]

(Link failure) --- does it mean cable failure ? check cable please

[mradul1811]

I am not sure about cable issue. I have me fully sure before telling this to site person