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Cant make  the 3COM 3C17300 4226T or LINKSYS SLM224g switch to work with a Cisco 2960G Switch

Hexagon Mining
Last Modified: 2008-08-08
Cant make the 3COM 3C17300 4226T or LINKSYS slm224g switch to work with a Cisco 2960G Switch. Ports 16 is configured with switchport access vlan11 and switchport mode access..(config. from switch entered below) As soon as switch is connected and turned on, LED blinks for once and goes dark....

Sw2#show running-config
interface GigabitEthernet0/16
 switchport access vlan 11
 switchport mode access
 spanning-tree portfast

Sw2#show interface gigabitEthernet 0/16
GigabitEthernet0/16 is down, line protocol is down (notconnect)
  Hardware is Gigabit Ethernet, address is 001b.2a95.0e10 (bia 001b.2a95.0e10)
  Description: 3COM Switch Port VLAN11
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Auto-duplex, Auto-speed, 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 never, output 31w0d, output hang never
  Last clearing of "show interface" counters never
  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 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     15866 packets input, 1399849 bytes, 0 no buffer
     Received 9901 broadcasts (0 multicast)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected
     2007963 packets output, 202293090 bytes, 0 underruns
     0 output errors, 0 collisions, 1 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

Sw2#show port-security interface gigabitEthernet 0/16
Port Security              : Disabled
Port Status                : Secure-down
Violation Mode             : Shutdown
Aging Time                 : 0 mins
Aging Type                 : Absolute
SecureStatic Address Aging : Disabled
Maximum MAC Addresses      : 1
Total MAC Addresses        : 0
Configured MAC Addresses   : 0
Sticky MAC Addresses       : 0
Last Source Address:Vlan   : 0000.0000.0000:0
Security Violation Count   : 0

What do you think guys ?
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"spanningtree bpduguard" config. from 2960 :

spanning-tree mode rapid-pvst
spanning-tree portfast bpduguard default
spanning-tree extend system-id
spanning-tree vlan 1-4092 priority 28672

and i dont think it is going to error-disabled mode. I was suspecting if a port security was enabled but as you can see from above that it isn't.


  • By enabling STP portfast,  are the devices behind the ports not allowed to influence the STP topology ? Does this end up by disabling the port upon reception of BPDU ? or the port is transitioned into error disable state ?
  • 3COM switch is unmanageable but LINKSYS is manageable.(web console)
  • i thought about trying different cross over cable ..will do that tom. morning.

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You guys were right, its going to err_disable mode

.00:01:21: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/24, changed state to up
00:01:21: %LINK-3-UPDOWN: Interface Port-channel1, changed state to up
00:01:22: %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel1, changed state to up
01:02:32: %SPANTREE-2-BLOCK_BPDUGUARD: Received BPDU on port GigabitEthernet0/16 with BPDU Guard enabled. Disabling port.
01:02:32: %PM-4-ERR_DISABLE: bpduguard error detected on Gi0/16, putting Gi0/16 in err-disable state

so disable bpduguard.
in normal corporate environment you shouldn't have wrong bpdus.

spanning-tree portfast bpduguard default

This command enables BPDUGuard by default on any port that has spanning-tree portfast configured. Since you had portfast configured on Gig0/16, the BPDUs from the 3Com/Linksys switch was causing the port to go to err-disable.


Shortly, disabling the portfast on Port0/16 will resolve the problem ? is there anything i need to be concerned about ?
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I appreciate you guys for working with me to resolve this issue....Have a good one. :)

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