Catalyst 2960X Trunk Uplink - ETHCNTR-3-LOOP_BACK_DETECTED

Hy,
I have a problem with the new Catalyst 2960X Series (WS-C2960X-48FPS-L; IOS 15.0(2)EX5; C2960X-UNIVERSALK9-M).
If I trying a trunk-port-channel to the core switch in VSS-Mode( Catalyst 6509E, Version 15.1(2)SY), go short time all trunk port interface to err-disable state ... 1 interface remains up state:
Feb 13 07:47:50.459: %ETHCNTR-3-LOOP_BACK_DETECTED: Loop-back detected on GigabitEthernet1/0/50.
Feb 13 07:47:50.459: %PM-4-ERR_DISABLE: loopback error detected on Gi1/0/50, putting Gi1/0/50 in err-disable state
Feb 13 07:47:51.504: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/50, changed state to down
Feb 13 07:47:52.539: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/50, changed state to down
... and so on ...
Config on the C2960X:
=================
interface Port-channel1
switchport mode trunk
no keepalive
end
interface GigabitEthernet1/0/49-52
switchport mode trunk
channel-protocol lacp
channel-group 1 mode passive
end
==================
Config on C6509E:
==================
interface Port-channel56
switchport
switchport mode trunk
end
interface GigabitEthernet1/3/6, 1/4/6, 2/3/6, 2/4/6
switchport
switchport mode trunk
channel-protocol lacp
channel-group 56 mode active
end
==================
Only if I make a shutdown and no shutdown on the err-disable interface comes up the port.
After a reload, the same goes all over again.
Does anyone have any idea or solution?
Regards and thanks for help...
Stefan

Hello, gropper1929.
I think spanning tree protocol detects a loop befoure your C6509E sends a request to form a aggregate channel (spanning tree works first after turning on the interface and prevent any traffic for 50 sec). Try to use active mode from a C2960X side too. Maybe it will help with your problem. Or you can configure err-disable for a 30 sec so after geting error it'll go up after 30 sec and form a aggregate channel.
Best Regards.

Similar Messages

Datacenter outage. %ETHCNTR-3-LOOP_BACK_DETECTED

Hi
This is big, i have a problem in one datacenter, and i really need some help. I already open a TAC case but meanwhile i want to discuss this problem that i`m facing. Come on guys, this is big. I have a datacenter like in the diagram, in the diagram i have only two rack but in reality there are more . We are migratig some machines from phisical to virtual (vmware). This is the diagram
I have a core of mixted 2X3750G and X using the latest IOS. One of the G switches is the master of the stack.
The design worked ok for some weeks then suddenly almost all the 3012 etherchannel uplinks goes into Err-disable with this error.
%ETHCNTR-3-LOOP_BACK_DETECTED: Keepalive packet loop-back detected on FastEthernet0/3.
%PM-4-ERR_DISABLE: loopback error detected on Fa0/3, putting Fa0/3 in err-disable state
%ETHCNTR-3-LOOP_BACK_DETECTED: Keepalive packet loop-back detected on FastEthernet0/3.
%PM-4-ERR_DISABLE: loopback error detected on Fa0/3, putting Fa0/3 in err-disable state
(of course i`m using gigabit ,the error message is copy paste from some documentation but the error is the same)
The only workaround was to disable the keepalives on that interfaces. I run some testing on cables all the test were fine. I looked into spanning tree problems/logs everything is fine.As soon as i put the keepalives back on 3012 etherchannel interfaces the port enters err-disabled state.
Any ideeas ?
PS I`m no vmware guy but is there any chances that some virtual machines caused this ?

Hello Adrian,
I am not aware of any interoperability issues. Then again, I am not using them myself and I am merely reflecting upon my best knowledge and overview of what issues have been discussed on these forums so far.
The information about the ports going to err-disabled state in seconds means that the ports receive their own LOOP frames back in seconds which is quite interesting - the LOOP frames are sent infrequently, once every 10 seconds or so. Is the time between reactivating the keepalive and err-disabling the port shorter than 10 seconds?
Anyway, questions and suggestions to play with:
What kind of STP are you using? Are there any special features, protections or guards implemented (PortFast, UplinkFast, BackboneFast, BPDU Loop Guard, UDLD, ...)?
How are the uplinks between blade switches and the stack configured - are they trunks or access ports? Are the usual settings correct - encapsulation, native/access VLAN, identical list of allowed VLANs, ...?
On the blade switch, look up the MAC address of the particular switchport that got err-disabled in the past (use the show interface command on the blade switch and look for the "bia" string). Then, on the switch stack, look up this MAC address in the CAM table. What port is it learned on? Is it pointing back to the correct port on the blade switch, or at least back the correct Port-channel interface?
Using the MAC address of the blade switch' port that got err-disabled, enter the following command on the stack:
show platform forward INTERFACE M.M.M M.M.M
where INTERFACE is the physical switchport on the stack that is connected back to the formerly err-disabled port on the blade switch, and M.M.M is the MAC address of the blade switch' port. You may also verify using the show mac address-table address M.M.M that this MAC address is indeed learned on the physical interface or on a Port-channel interface that includes this physical switchport. The point of the show platform command is to verify if this switch is going to forward the frame or drop it - naturally, it should drop it. The switch should produce a rather lengthy output that should end with the following statement: "Dropped due to failed deja vu check.". If any other output is produced, I would need to see the output in its entirety.
Using the show mac address-table learning, verify on each switch that the learning of MAC addresses has not been disabled on any of your VLANs.
Verify using the show controllers utilization if any of the ports shows excessive utilization - that would suggest a switching loop in progress.
Consider activating UDLD Agressive on all physical switchports between the blade switch and the stack. UDLD is also capable of detecting a looped port and could perhaps provide additional information. You can implement UDLD gradually, on a per-port basis and see if it brings down the port, and if so, with what explanation.
Best regards,
Peter

Does the Catalyst 2960x-48TD support Cisco's IGMP Snooping MIB?

Does the Catalyst 2960x-48TD support Cisco's IGMP Snooping MIB? We have a number of switches from different vendors and have recently begun switching to Cisco's, however unlike the other brands I am unable to audit the IGMP Snooping settings via SNMP. It appears that while the switch supports IGMP Snooping it does not support the CISCO MIB for IGMP Snooping. Is this a known bug and is it fixed in any of the later releases?
Our company is purchasing and deploying C2960X-48TD's and I am tasked with updating our system audit software

Hi Sean,
Nov 21 15:40:42.390: %MCAST-SPSTBY-6-ETRACK_STATS_LIMIT_EXCEEDED: Number of entries in IGMP snooping explicit-tracking statistics has exceeded the maximum limit (32000)
The above log message is written because the number of explicit-tracking statistics entries is bounded to avoid monopolizing of system resources by IGMP/MLD snooping. The explicit-tracking statistics database maximum size is set to the same as that of explicit-tracking limit.
The statistics are split into two banks: permanent and volatile. The statistics entries will be stored permanently (volatile) until the permanent entries threshold is reached, after which the statistics will be stored temporarily up to the database maximum size. When the size of the database exceeds the permanent threshold, a group will be removed on receiving an IGMP/MLD leave. Groups can be removed whether they were installed above or below the permanent threshold. If the number of statistics entries grows beyond the maximum size of the database, then no statistics will be stored for any newly formed groups.
You can disable ip igmp snooping explicit-tracking by the following
1) Configure "no ip igmp snooping explicit-tracking"
2) Configure "ip igmp snooping limit track 0" on global.
3) After ET is disabled, please do a "clear ip igmp snooping statistics".
Here is a reference URL (please make sure you copy and paste the entire link to the browser):
http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/snooigmp.html#wp1062242
HTH
Luke

ETHCNTR-3-LOOP_BACK_DETECTED

Guys,
I'm getting the following error message in my environment.. Can you please shed some light on this issue...
%ETHCNTR-3-LOOP_BACK_DETECTED: Loop-back detected on GigabitEthernet0/43.
%PM-4-ERR_DISABLE: loopback error detected on Gi0/43, putting Gi0/43 in err-disable state
Environment:
Got few 3560x and 3750x switches (Source) (GigabithEthernet) centrally connected to a pair of 3560x switches (Destination) on the GigabithEthernet ports...
On the Source switches, the Gi ports are configured as Access ports and IP is assigned on the SVI for that particular VLAN... On the Destination Switch, the switchports are configured as Private VLAN - Isolated...
The Interlink between Destination Switches allows only the private VLAN numbers and native vlan...
Issue:
I receive the above mentioned logs on the Source switches and the ports go err-disabled... If I've 3 source switches, only one port is UP and rest of the 2 Source switch ports go to err-disabled... If I shut and no shut any one of the err-disabled port, the previously UP port goes into err-disabled port while the new port comes up...
Searched through few forums and I found that it could be due to some faulty cables or Keepalive being received on the same port... I tried changing the cables but no use... Disabling keepalive would be an ugly workaround as it doesn't help me to find the root cause...
IOS Version: 15.2(1)E1
Regards,
Sri

Sri
I had a situation where we were receiving that error message. I tracked it down to a vlan mismatch on one of the other switches in the network (not the one where I was receiving the error message). There was actually a layer 2 loop created but Spanning Tree did not detect the loop and it was allowing the keepalive from my interface to be forwarded back to the originating interface and causing it to be errored out. Spanning Tree did not detect the loop because one side was sending BPDUs for vlan 2 but the other side was in vlan 3 and did not process the BPDU and therefore did not detect the loop. It sounds to me like you may have a similar issue in terms of vlan mismatch.
HTH
Rick

Catalyst 2960X-48 is not displayed in CiscoView

Hi all,
the customer uses LMS 4.2.4. He has the latest package for Cisco View (Cat2960.cv50.v18-0.zip) installed. When he try to display Cat2960X with 48 ports the Cisco View shows nothing. Cisco View shows the Catalyst 2960X-24 without any problems. It seems that Cisco View doesn't support Cat2960-48 in the latest package. Is some solution for this problem?
Thank you
Roman

Hi, I installed the latest packages also and i´m using WS-C2960X-48LPD-L 15.0(2)EX4.
It seem Cisco Prime LMS doesnt support it, I can´t see nothing in CiscoView.
It´s a huge problem.

Cisco Catalyst 2960X-24PS-L - Management Issues

I am having issues connecting to the new Cisco Catalyst 2960X-24PS-L switches via USB.
I am successfully connecting from the same PC to Cisco 2960C series and Cisco 2960S switches, but the 2960X switches aren't always working.
Any hints?
Matt

So I was able to get it working:
Updated to latest version of Putty, connected something to a switch port and then made sure flow control was off.
A bit different than the older switches.

Cisco Catalyst 2960X-48FPD-L Whit SFP+ 10GB

Hello!!
Can i use 10Gb Link between a Cisco Catalyst 6500 whit a Cisco Catalyst 6900 Series 8-Port 10 Gigabit Ethernet Fiber Module (WS-X6908-10G-2T) card and 10GBASE-SR X2 Fiber port, and . And in the other side use a Cisco Catalyst 2960X-48FPD-L (have two SFP+ bays) whit SFP-10G-SR=  (multimode fiber)
this solutions works???
another question:
WS-X6908-10G-2T card   comes equipped with DFC4. What mean that? requiere another slot in a 6500 chassis??
thanks

Hi,
Q1:- yes it should work.
http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-6500-series-switches/data_sheet_c78-648212.html
2)
WS-X6908-10G-2T card   comes equipped with DFC4. What mean that? requiere another slot in a 6500 chassis??
Answer: No DFC4 is the sub-module which would sit on the line card WS-X6908-10G-2T. It doesnt require any spare slot.
WS-X6908-10G-2T: comes equipped with DFC4 for distributed forwarding, supporting 256K forwarding entries, increased ACL entries to 64K, increased Netflow entries to 512K, and increased IPv4 forwarding speed to 60 Mpps
HTH

Cisco Prime Infrastructure 2.2: Catalyst 2960X-24TS-LL Switch Collection Failure

Hello,
I've Upgraded Prime Infrastructure to Version 2.2.0.0.158. Now our Catalyst 2960X-24TS-LL switches show an error message, when they are added to the inventory. The error is as follows:
Partial Collection Failure; Collection Status : Failed feature(s).
The 2960X-24TS-LL is listed under the supported devices list and other switches (e.g. WS-C2960X-48FPS-L) got inventorized without any problems.
Did anybody see this issue and can tell me how to solve it.
- Benjamin

- Getting that one too, since running 2.2 (Failed Features) ; suggest opening a TAC case.
M.

Cisco PI 2.1 cannot add catalyst 2960x

hi all,
I have Cisco PI1.2 i upgraded it to 2.1 and after it up i found its version is "Version : 2.1.0.0.87"
i tried to add 2960x but i failed
I searched and find that I have to install the patch pi211_20140630_01.ubf using GUI not using CLI and after I checked that is successfully upgraded as per the upgrade guide
i found the PI version is still 2.1.0.0.87 and cannot add the 2960x switch
please advice
thanks in advance.

What device packs do you have installed on Prime? (Device packs are different from patches.)
Prime GUI - Administration - Software Update
Device Pack 6 was just released (10/31/14)

STACK mode vs HSRP - Catalyst 2960X

Hi
Short question.
I have below topology with hardware on board: WS-C2960X-24TD-L 15.0(2)EX4 C2960X-UNIVERSALK9-M
Question:
What solution will be the best STACK or HSRP ?
At the moment issue is that, when one 3rd router will go down, there is no HA between 2960X, Im loosing connection.
Below interfaces from 2960X are going to 3rd router WAN connection.
#sh run int gi 1/0/9
Building configuration...
Current configuration : 66 bytes
interface GigabitEthernet1/0/9
switchport access vlan 210
end
#sh run int gi 2/0/10
Building configuration...
Current configuration : 67 bytes
interface GigabitEthernet2/0/10
switchport access vlan 210
end

Thank you for the additional information. It answers some questions and raises some other questions.
Probably most important thing is that the routers are from different ISPs and run independently. That establishes that HSRP between the routers is not an option. It does raise the question that if the routers are from different ISPs then they probably have different IP addresses and subnets. So why are both routers on the same VLAN on the switch? Being in the same VLAN usually implies being in the same subnet. But it seems unlikely that both routers are really in the same subnet if they are from different ISP. Perhaps you can clarify this?
HSRP is not an option on these switches. HSRP is a layer 3 redundancy protocol and these switches are layer 2 switches as far as I know. And I do not see anything in the description of the problem that suggests that the switch feature set is an issue.
Here is the statement of the problem from the origial post.
when one 3rd router will go down, there is no HA between 2960X, Im loosing connection.
If one 3rd party router goes down then there will be no connectivity through it and there is not anything that your switch can do about that. If the routers are from different ISP then compensating for failure of one router is a question of routing. And it is not clear what you are doing about routing in this situation. Probably we need more information about how your routing is set up.
HTH
Rick

Cisco Catalyst 2960X Ethernet Switch

"I want to buy Catalyst 2960-X series switches like WS-C2960X-24PS-L,WS-C2960X-24PD-L, buy I'm not very well know about c2960x series. Can someone help me ?"--from yahoo answer.
All Catalyst 2960-X Series Switches use a single Universal Cisco IOS Software Image for all SKUs.Cisco Catalyst 2960-X Family of Switches are available with the LAN Base and LAN Lite feature sets.
WS-C2960X-24PS-L Overview
Catalyst 2960-X 24 GigE PoE 370W, 4 x 1G SFP, LAN Base Switch
WS-C2960X-24PD-L Overview
Catalyst 2960-X 24 GigE PoE 370W, 2 x 10G SFP+, LAN Base Switch

If you buy the LAN Base model, you'll have all of Cisco's normal switching features and options. My company has purchased many of these switches, and they work very well. Remember, these are access layer switches. If you're looking for something to be an aggregate switch for things that push a lot more data (ex. several wireless controllers), you'll want to go for something more powerful.

Multiple Catalyst 2960X-48LPS-L needing constant reboots

So here's the situation:
Single building with known power issues (I really mean it, a light bulb won't stay on for a consistent 12 hours). We have 5 2960X-48LPS-L switches in the building with minor configuration at this point (just TACACS+, NTP servers, static IP, SSH cert, etc). We run into an issue where they seem to cause the end users to not be able to do anything (Windows clients show limited connectivity). Usually by the time we (Network Operations) get notified, they've hard-rebooted the switch like a cheap Linksys so we can't effectively troubleshoot.
We have the exact same model of switches in a large number of offices and have never had this issue. All are running the same IOS version and everything.
Any ideas? Or are these switches extremely sensitive to possible power drops? If they are, I'll have to have an electrician check the building out as I will not touch anything over 48 volts/1 amp.
Thanks
Some diagnostic information:
show ver output:
Switch Ports Model SW Version SW Image
* 1 52 WS-C2960X-48LPS-L 15.0(2)EX5 C2960X-UNIVERSALK9-M
and show proc cpu his
333333333333333333333333334444433333333333333333333333333333
988888999999999988888888881111188888888889999977777888887777
100
90
80
70
60
50
40 **********************************************************
30 **********************************************************
20 **********************************************************
10 **********************************************************
0....5....1....1....2....2....3....3....4....4....5....5....6
0 5 0 5 0 5 0 5 0 5 0
CPU% per second (last 60 seconds)
444444444344444444444443444344444444344434434443444433434344
110000005903300010001009001910221000900190890019000199090900
100
90
80
70
60
50 * *
40 ##########################################################
30 ##########################################################
20 ##########################################################
10 ##########################################################
0....5....1....1....2....2....3....3....4....4....5....5....6
0 5 0 5 0 5 0 5 0 5 0
CPU% per minute (last 60 minutes)
* = maximum CPU% # = average CPU%
545454554454544547
180729104608339290
100
90
80
70 *
60 *
50 ******** **** ****
40 ##################
30 ##################
20 ##################
10 ##################
0....5....1....1....2....2....3....3....4....4....5....5....6....6....7..
0 5 0 5 0 5 0 5 0 5 0 5 0
CPU% per hour (last 72 hours)
* = maximum CPU% # = average CPU%

15.0(2)EX5
Due to stability issue, use 15.0(2)EX3.

Keepalive and layer 2 loopback detection

My question is concerned with how Cisco switches use keepalive at layer 2 to detect loopbacks. All the info on keepalive that I could find was concerned with its use at higher layers (eg tunnels, routing protocols etc).
We had an incident where a mismatch in switch configurations caused a loop that wasn't blocked by spanning tree. This caused a number of our switches to err-disable their uplinks "%ETHCNTR-3-LOOP_BACK_DETECTED: Keepalive packet loop-back detected". Some of these switches where fairly deep down a chain of switches with only a single uplink path.
We have also had a situation (which eventually went away) where the single uplink on a particular switch was err-disabled loopback detected although we could find no evidence of a loop. I have my suspicions about keepalive packets not being dealt with properly especially if vlan 1 is removed from trunk links (which we have to do in some cases) or ether channels are involved. Bugs CSCeg58877 and CSCdt82690 describe such problems but neither of these match our circumstances.
Because of the above I am considering disabling keepalive on my Cisco switches layer 2 links, especially uplinks, is this a good or bad idea?
Alex McLaren

Hi Alex-
Loopback detection was a mechanism that was put in place to detect loops in the network
caused by Type1a or tyep2 copper cabling. While it is a good mechansim for those special
situations , there seems to be no need for having it enabled on the Gig ports where you
can use features like UDLD to detect a fiber loop or unidirectional fiber.
But in 12.1EA releases , loopback detection is enabled by default on the fiber ports as
well as copper ports. On some fiber ports , neighboring switch may just switch the
keepalive packet back w/o making any change in the packet causing the original switch that
sent out the keepalive to recive its own packet back kicking in this mechanism of
error-disabling the port.
What you can do is you can disable keepalives on the uplink Gig ports of the 2950 and that
should take care of the problem
On 2950
int gig
no keepalives
But make sure you have UDLD enabled. Once you have disabled the keepalives , please make
sure you have low cpu on the 2950s that were showing the problem as well as make sure the
mac-aging timer stays at 300 sec.
show proc cpu
show mac- aging
UDLD should however be enabled on fiber Gig ports to detect spanning tree loop problems.
Keepalive detection mechansim is speciafically there for Type1a and type 2 cabling and has
no significance on fiber ports.
This is also documented in the the release notes of the following Cisco DDTS id #
CSCea46385.
An interface on a Catalyst switch is errordisabled after detecting a loopback.
Mar 7 03:20:40: %ETHCNTR-3-LOOP_BACK_DETECTED: Loop-back detected on GigabitEthernet0/2.
The port is forced to linkdown.
Mar 7 03:20:42: %LINK-5-CHANGED: Interface GigabitEthernet0/2, changed state to
administratively down
Mar 7 03:20:43: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/2,
changed state to down
Conditions:
This might be seen on a Catalyst 2940, 2950, 2950-LRE, 2955, 2970, 3550, 3560 or
3750 switch running 12.1EA or 12.2SE based code.
Workaround:
Disable keepalives by using the "no keepalive" interface command. This will
prevent the port from being errdisabled, but it does not resolve the root cause of
the problem. Please see section below for more information.
Additional Information:
The problem occurs because the keepalive packet is looped back to the port that sent
the keepalive. There is a loop in the network. Although disabling the keepalive
will prevent the interface from being errdisabled, it will not remove the loop.
The problem is aggravated if there are a large number of Topology Change Notifications
on the network. When a switch receives a BPDU with the Topology Change bit set,
the switch will fast age the MAC Address table. When this happens, the number of
flooded packets increases because the MAC Address table is empty.
Keepalives are sent on the Catalyst 2940, 2950, 2950-LRE, 2955, 2970, 3550, 3560
or 3750 switch to prevent loops in the network. The primary reason for the keepalives
is to prevent loops as a result of Type 2 cabling. For more information, see:
http://www.cisco.com/en/US/netsol/ns340/ns394/ns74/ns149/networking_solution
s_white_paper09186a00800b4249.shtml
Keepalives are sent on ALL interfaces by default in 12.1EA based software. Starting
in 12.2SE based releases, keepalives are NO longer sent by default on fiber and uplink
interfaces. Since there is no 12.2SE release for 2950s , you will have to manually disable
the keepalives on uplink Gig ports.
Hope this helps.
thanks
Salman Zahid

Catalyst 2960 uplink ports

Hi,
is there any difference between uplink ports (using 1Gbps SFP) and any another 10/100/1000 port on Catalyst 2960X ? What I mean is: if uplink port has a 1Gbps SFP and considering that standard port are 10/100/1000, is there a reason, for example related to Catalyst internal hardware and bus architecture, that should make me connect a server to the uplink port instead to any another port ?
Thank you a lot,
enrico.

Although you can purchase Copper SFP's, people generally use the SFP ports on a switch to connect fibre cables to which means they they get the full 12/24/48 ports for their hosts.
Using one or more of the standard ports for uplinks means there are less for hosts but if you have spare and don't want the cost of running fibre and purchasing additional SFP's then use the normal ports.

Uplink going down

At our campus we have strange issue with 3550 switch. This switch has always blocked uplink port (this is connected via trunk) - port is always shutdown - after restart (or when is port manualy set to up) few hours is everything OK - but uplink port is blinkink very fast, but later port is disabled again. Any ideas, some STP issue any ideas how to fix it???? We have this problem with two switches and both are 3550.....

I found in log
%ETHCNTR-3-LOOP_BACK_DETECTED: Loop-back detected on GigabitEthernet0/1. The port is forced to linkdown.
Cisco says to this
These messages are a result of a failure of the switch software when trying to program the hardware.
Most of these errors lead to incorrect switch behavior, and you should call your Cisco technical support representative."
Error Message ETHCNTR-3-LOOP_BACK_DETECTED: Loop-back detected on [chars].
Explanation This message means that a loopback condition might be the
result of a balun cable incorrectly connected into a port. [chars] is the
interface name. Recommended Action Check the cables. If a balun cable is connected and
the loopback condition is desired, no action is required. Otherwise, connect
the correct cable, and then enable the port."

Catalyst 2960X Trunk Uplink - ETHCNTR-3-LOOP_BACK_DETECTED

Similar Messages

Maybe you are looking for