GigabitEthernet1/1 is up, line protocol is down (notconnect)

Question

Hi All,
I am really curious to investigate a possible reason behind this error message.
During the configuration of a port channel bundled with 2 links I have the error in the subject but only for one side of the connection and only for one link part of the port channel.
On the other side the corrispondent interface was up/up and the other link part of the port channel was able to go up with no issue (for all the configuration is the same).
Background info:
- The link in discussion was connecting the two Multilayer swicthes before the configuration of the port channel with no issue
- The port channel is a L2 etherchannel
- What was done was simply to shutdown the interface on both swicthes, add the command channel group xx mode on  on both side of the connection and then bring up the connection with the result above showed: one side up/down (not connect) and the other side up/up
I am excluding problem with the configuration. The reason is simple: i just reply the configuration to the all links (total 2) part of the port channel with no issue.
Can be a cabling problem (SFP)? Again keep in mind that before the change, this link was active with no issue for 4 years.
Thanks all.

Answer 1

Hi Peter,
Find below the requested output.
I forgot to mention something:
The etherchannel is a L2
The mode employed to create the port channel was on
In any case what I did in the meanwhile was:
- To check the cable -> It is ok
- I did not check the SFP but I configured the involved interfaces as L3 and I bringed up both with no issue. They are connected so I am assuming that the SFP is ok. Do you agree?
At this point due to the fact that:
Configuration is working properly for the second link part of the same portchannel
The cable and sfp is ok
The only problem that I can see here is the Etherchannel Modes adopted: I heard that on modes is not the best practice. The best is use the LACP
Here the requested output:
show int gi1/1 capa
Dot1x:                 yes
  Model:                 WS-X6748-SFP
  Type:                  1000BaseSX
  Speed:                 1000
  Duplex:                full
  Trunk encap. type:     802.1Q,ISL
  Trunk mode:            on,off,desirable,nonegotiate
  Channel:               yes
  Broadcast suppression: percentage(0-100)
  Flowcontrol:           rx-(off,on,desired),tx-(off,on,desired)
  Membership:            static
  Fast Start:            yes
  QOS scheduling:        rx-(1q8t), tx-(1p3q8t)
  CoS rewrite:           yes
  ToS rewrite:           yes
  Inline power:          no
  SPAN:                  source/destination
  UDLD                   yes
  Link Debounce:         yes
  Link Debounce Time:    yes
  Ports on ASIC:         25,27,29,31,33,35,37,39,41,43,45,47
  Port-Security:         yes
GigabitEthernet1/1 is up, line protocol is down (notconnect)
  Hardware is C6k 1000Mb 802.3, address is 0019.aa70.0000 (bia 0019.aa70.0006)
  Description:
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, media type is SX
  input flow-control is off, output flow-control is off
  Clock mode is auto
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:58, output 02:08:13, output hang never
  Last clearing of "show interface" counters 4y10w
  Input queue: 0/2000/66318/0 (size/max/drops/flushes); Total output drops: 1731225685
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 17000 bits/sec, 25 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     1705750435550 packets input, 2106584160022948 bytes, 1 no buffer
     Received 245618852 broadcasts (148781910 multicasts)
     0 runts, 48 giants, 1 throttles
     0 input errors, 0 CRC, 0 frame, 66317 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected
     3762458417011 packets output, 3133012553118384 bytes, 0 underruns
     0 output errors, 0 collisions, 4 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 PAUSE output
     0 output buffer failures, 0 output buffers swapped out
show interfaces status err-disabled
empty
show etherchannel summary
120    Po120(SU)        -        Gi1/2(P) Gi1/1(D)