Interface Resets/Problems

nkillgorenkillgore Member Posts: 67 ■■□□□□□□□□
I've got an interface on a switch that is connected to a L2VPN from our ISP. The connection to the ISP has dropped 3 times now right in the middle of our backups (I think we are pushing about 600-700 Mbps over the 1Gb circuit for several hours in the middle of the night). These drops started after we began utilizing the circuit heavily. Prior to this time period, we probably were not using more than about 100Mbps.

I noticed tonight that the interface resets counter is at 2. None of the other counters show anything. The topology goes something like (My switch --- Media Converter (Provider owned) --- Provider Edge). The third time there was an outage, the interface went into an errdisabled state while the carrier was troubleshooting.

Any ideas? Could it be the media converter? The ISP is saying it's our equipment and does not seem to want to troubleshoot further until we prove that it is not. I've included sh run and sh int of the interface below.

interface GigabitEthernet0/20
switchport trunk allowed vlan 32,51,172
switchport mode trunk
switchport nonegotiate
speed 1000
duplex full

GigabitEthernet0/20 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is 001e.f6c0.2c94 (bia 001e.f6c0.2c94)
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 17/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 1000Mb/s, media type is 10/100/1000BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 2d15h, output 00:00:00, output hang never
Last clearing of "show interface" counters 19w6d
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 70146000 bits/sec, 5927 packets/sec
5 minute output rate 1942000 bits/sec, 3142 packets/sec
22233773926 packets input, 19310005575705 bytes, 0 no buffer
Received 10910808 broadcasts (0 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 1269279 multicast, 0 pause input
0 input packets with dribble condition detected
21787744742 packets output, 15752863272890 bytes, 0 underruns
0 output errors, 0 collisions, 2 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


  • fredrikjjfredrikjj Member Posts: 879
    A major problem is that many people are also hard setting Gigabit Ethernet , and this is causing major problems. Gigabit Ethernet must have auto-negotation ENABLED to allow negotiation of master / slave PHY relationshitwhp for clocking at the physical layer. Without negotiation the line clock will not establish correctly and physical layers problems can result.
    Autonegotiation on Ethernet - it works, it should be mandatory!
  • nkillgorenkillgore Member Posts: 67 ■■□□□□□□□□
    Interesting. The carrier specifically asked us to set it to 1000/full (I even have an email proving it!!) I will talk to them about this.

  • fredrikjjfredrikjj Member Posts: 879
    I'm also skeptical of the use of a media converter. Maybe it can't handle that kind of load. How would you know if it is failing since it (probably) doesn't have any kind of diagnostics running that you are able to access, etc. And the carrier probably can't troubleshoot it in any other way besides replacing it, which they are probably hesitant to do.
  • networker050184networker050184 Mod Posts: 11,962 Mod
    Is the actual physical connection going down? Do your logs show it? If so I'd take that to the provider and have them look into it.
    An expert is a man who has made all the mistakes which can be made.
  • chob11chob11 Member Posts: 26 ■□□□□□□□□□
    Your interface probably went into errdisabled state due to possible loopback detected on interface. Some media converters can be programmed to go into loopback state when it loses carrier on other interface. Media converters can also be programmed to drop carrier on one interface if it loses carrier on other. I would go back to your ISP and verify the connection on their end of media converter is not taking any input errors.
  • nkillgorenkillgore Member Posts: 67 ■■□□□□□□□□
    Just an update. Logs on our switch verified that the connection went into errdisabled because a loopback was detected. The carrier has agreed to get rid of the media converter and connect to us directly via fiber!

    The carrier said that they had zero troubleshooting capabilities on the media converter. We eventually convinced them that if we couldn't see anything wrong on our side, they couldn't see anything wrong on their side, and they had no visibility on the media converter, then the likely culprit was the media converter. Hopefully this is a solution.

    Thanks for the suggestions.
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