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New Member

Detected a LoopBack & Port has been Disabled

Have a nice day,

We have a LAN setup of 18no.s of Cisco 2950 & 2960 switches with 7no.s of Cisco 1131 AP along with Ruckus AP. All these devices are connected to Cisco Catalyst 4507R L3 Switch.

Now from past 3 days all fibre uplinks in each switch are getting disabled once a day.

"spanning-tree portfast" has been enabled for all single users ports & "spanning-tree link-type point-to-point" has been enabled between switch uplinks.

below attached is the 4507R switch log.

L3SWITCH#sh log
Syslog logging: enabled (0 messages dropped, 1 messages rate-limited, 0 flushes,
0 overruns)
    Console logging: disabled
    Monitor logging: level debugging, 0 messages logged
    Buffer logging: level debugging, 250 messages logged
    Exception Logging: size (8192 bytes)
    Count and timestamp logging messages: disabled
    Trap logging: level informational, 250 message lines logged

Log Buffer (4096 bytes):
PING: Host 00:24:1D:66:4E:7F in vlan 7 is flapping between port Gi3/3 and port Gi1/1
1d12h: %C4K_EBM-4-HOSTFLAPPING: Host 00:26:73:54:ED:94 in vlan 7 is flapping between port Gi1/1 and port Gi3/3
1d12h: %C4K_EBM-4-HOSTFLAPPING: Host 00:24:1D:66:4E:7F in vlan 7 is flapping between port Gi3/3 and port Gi1/1
1d12h: %C4K_EBM-4-HOSTFLAPPING: Host 00:90:E8:23:19:8D in vlan 11 is flapping between port Gi3/3 and port Gi3/1
1d12h: %C4K_EBM-4-HOSTFLAPPING: Host D4:BE:D9:EB:62:6B in vlan 11 is flapping between port Gi3/5 and port Gi3/6
1d12h: %C4K_EBM-4-HOSTFLAPPING: Host 00:90:E8:23:19:8D in vlan 11 is flapping between port Gi3/3 and port Gi3/1
1d12h: %C4K_EBM-4-HOSTFLAPPING: Host 00:90:E8:23:19:8D in vlan 11 is flapping between port Gi3/3 and port Gi3/1
1d12h: %C4K_EBM-4-HOSTFLAPPING: Host D4:BE:D9:EB:62:6B in vlan 11 is flapping between port Gi3/5 and port Gi3/6
1d12h: %C4K_EBM-4-HOSTFLAPPING: Host 00:90:E8:23:19:8D in vlan 11 is flapping between port Gi3/3 and port Gi3/1
1d12h: %C4K_EBM-4-HOSTFLAPPING: Host 00:90:E8:34:84:1E in vlan 11 is flapping between port Gi3/5 and port Gi3/4
1d12h: %C4K_EBM-4-HOSTFLAPPING: Host D4:BE:D9:EB:62:6B in vlan 11 is flapping between port Gi3/3 and port Gi3/6
1d12h: %C4K_EBM-4-HOSTFLAPPING: Host 00:90:E8:24:D5:93 in vlan 11 is flapping between port Gi3/5 and port Gi3/4
1d12h: %C4K_EBM-4-HOSTFLAPPING: Host 00:90:E8:23:19:8D in vlan 11 is flapping between port Gi3/3 and port Gi3/1
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host D0:67:E5:08:18:61 in vlan 5 is flapping between port Gi3/5 and port Gi3/2
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host 3C:4A:92:D4:3D:BC in vlan 5 is flapping between port Gi3/2 and port Gi3/3
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host BC:30:5B:C1:70:2A in vlan 5 is flapping between port Gi3/1 and port Gi3/5
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host BC:30:5B:C1:6A:64 in vlan 9 is flapping between port Gi3/3 and port Gi3/2
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host F0:4D:A2:F7:CC:5D in vlan 9 is flapping between port Gi3/3 and port Gi3/1
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host 00:23:AE:A9:2F:C0 in vlan 9 is flapping between port Gi3/3 and port Gi3/5
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host BC:30:5B:AD:8F:D2 in vlan 9 is flapping between port Gi3/1 and port Gi3/5
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host BC:30:5B:C1:6A:64 in vlan 9 is flapping between port Gi3/3 and port Gi3/2
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host F0:4D:A2:F7:CC:5D in vlan 9 is flapping between port Gi3/1 and port Gi3/3
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host 00:23:AE:A9:32:B4 in vlan 9 is flapping between port Gi3/6 and port Gi3/5
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host F0:4D:A2:F7:CC:5D in vlan 9 is flapping between port Gi3/3 and port Gi3/1
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host BC:30:5B:AD:8F:D2 in vlan 9 is flapping between port Gi3/3 and port Gi3/1
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host 00:23:AE:A9:32:B4 in vlan 9 is flapping between port Gi3/3 and port Gi3/5
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host BC:30:5B:AD:8F:D2 in vlan 9 is flapping between port Gi3/1 and port Gi3/3
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host 00:23:AE:A9:32:B4 in vlan 9 is flapping between port Gi3/6 and port Gi3/3

2d01h: %C4K_EBM-4-HOSTFLAPPING: Host F0:4D:A2:F7:CC:5D in vlan 9 is flapping between port Gi3/1 and port Gi3/3
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host D0:67:E5:0A:80:45 in vlan 9 is flapping between port Gi3/1 and port Gi3/5
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host 00:90:E8:24:D1:20 in vlan 11 is flapping between port Gi3/5 and port Gi3/1
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host 00:90:E8:24:D1:20 in vlan 11 is flapping between port Gi3/3 and port Gi3/1
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host D4:BE:D9:EB:62:6B in vlan 11 is flapping between port Gi3/5 and port Gi3/6
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host 00:90:E8:24:D1:20 in vlan 11 is flapping between port Gi3/3 and port Gi3/1
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host 00:90:E8:24:D1:20 in vlan 11 is flapping between port Gi3/3 and port Gi3/1
2d01h: %C4K_EBM-4-HOSTFLAPPING: Host D4:BE:D9:EB:62:6B in vlan 11 is flapping between port Gi3/6 and port Gi3/5
2d02h: %C4K_EBM-4-HOSTFLAPPING: Host BC:30:5B:BC:11:59 in vlan 5 is flapping between port Gi1/2 and port Gi3/3

i have installed CNA for root cause finding & it gave below messages generated from AP

Description: Memory allocation of 1692 bytes failed from 0xFCD44, alignment 4

Explanation:  The requested memory allocation is not available from the specified "  "memory pool. The current system configuration, network environment, or "  "possibly a software error may have exhausted or fragmented the router's "  "memory. 

Recommended Action:  If you suspect a software error, copy the error message exactly as it "  "appears on the colsole or in the system log, contact your technical support"  "representative,and provide the representative with the gathered information. "  "Otherwise, you may need to add more memory or reduce the number of "  "features you are trying to support. 

Type: SYS-2-MALLOCFAIL

Description: Host 687f.7468.8c3d in vlan 5 is flapping between port Gi1/0/52 and port Gi1/0/51

Explanation:  not available

Recommended Action:  not available

Type: SW_MATM-4-MACFLAP_NOTIF

Request Support

6 REPLIES
New Member

Detected a LoopBack & Port has been Disabled

Hi!

can you share a Diagram?

I have seen this on my network, and sometimes has to do with a reset on the server and this has 2 connections to two switches ah we know the MAC on the access port and trunk? Not sure if the ports you mention like 3/3 is trunk?

actually is good that the port goes to disable, because this can bring you hole network down.

Probably you need to reduce the time the switch free the MAC ADDRESS? also is important to have defined the root?

Another Idea is to enable UDLD on the fibers so you can know if a fiber is wrong?

New Member

Detected a LoopBack & Port has been Disabled

Hi Rodrigo,

Here with attaching the network map & Error displayed in Cisco Network Assistant

New Member

Detected a LoopBack & Port has been Disabled

Hi Manoj


I can see a connection between swith 15.36 and 15.23 via 15.22.  This seems to be a possible loop in you topology.  Hence spanning-tree must take action block one path.

You need to find root switch in you network and check for block and forward ports.  My suggestion would be to make 15.10 to be root swtich for your network.

Or just to test disable connectivity between 15.36 and 15.22 and check if you are still getting those logs.

Regards
Bharat

Hall of Fame Super Gold

Detected a LoopBack & Port has been Disabled

spanning-tree link-type point-to-point

Your switch uplink has this?????  Wow.  That's one insane line I do not wish to see in my network.  It's outdated and outright dangerous.

What is your uplink like?  Is it fibre?  If it is fibre, you can optionally enable UDLD on both sides.  If it's copper, I'd stay away from enabling UDLD as it can potentially cause more issues.

New Member

Detected a LoopBack & Port has been Disabled

Hi Manoj!

Definetly first thing enable UDLD on both side.  If a fiber has a problem it will tell you

Thanks

REGP

Detected a LoopBack & Port has been Disabled

Hi

That's message is the last message you ever want to see in the switch logs.

%C4K_EBM-4-HOSTFLAPPING: Host 00:90:E8:24:D1:20 in vlan 11 is flapping between port Gi3/5 and port Gi3/1

It means that you have an spanning-tree loop, basically STP is confused and it can't calculate what port to block, as a consequence the switch will learn the same mac address across different ports cause traffic is not getting blocked... UDLD is troubleshooting for layer 1 issues, but you don't seem to have a layer 1 issue, it's a STP layer 2 issue. Check you STP configuration, root ports, designated ports, block ports, root switch....

Regards.

Wilson B.

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