Solved: Connecting 3750 and 3650 switches together

barnmichael · ‎09-17-2012

I have a small network using a 24 port 3750 switch. I need to add five computers in another room and only have one Cat 6 cable running there and no room left on the 3750. I got a 3650 to put in the new room with the new computers. The problem is, whenever I plug the new switch into the 3750, it shuts down the port and gives me an err-disable. I can do a shut/no shut and re-enable the port. I searched the web for help and read about trunking and clusters. I'm not sure which, if either, is appropriate. I see various documentation that shows you can put one switch behind the other. But nothing tells me the configuration which will allow it.

Any help would be appreciated. My Cisco knowledge is meager at best.

Thanks,

Michael

Peter Paluch · ‎09-17-2012

Michael,

The Gi1/0/8 port is currently configured for attachment of a single PC, and is specifically configured to prevent another switch from being attached.

My recommendation is to configure this port, and also the port on the 3560, as a trunk port, then create appropriate VLANs on the 3560 and assign the required ports on the 3560 to required VLANs.

The 3750 should be configured as follows (you may paste the following lines directly to the global configuration mode entered by the configure terminal command):

default interface gi1/0/8

interface gi1/0/8

switchport trunk encapsulation dot1q

switchport mode trunk

end

The port on the 3560 should be configured in an identical way, just the port name should be changed to gi0/24.

Are you familiar with creating VLANs and assigning access ports into them?

Best regards,

Peter

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Peter Paluch · ‎09-17-2012

Hello Michael,

We need to find out why the port gets err-disabled. It suggests an incorrect configuration. When the port is err-disabled, please issue the show int status err-disable command and post the output here.

Also, please, post the configuration of the port that gets err-disabled, and the configuration of the port on the neighboring switch. Thank you!

Best regards,

Peter

barnmichael · ‎09-17-2012

3750 error:

Port Name Status Reason

Gi1/0/8 err-disabled bpduguard

3650 port:

Switch#sh int gig 0/24

GigabitEthernet0/24 is down, line protocol is down (notconnect)

Hardware is Gigabit Ethernet, address is 0019.30e9.9698 (bia 0019.30e9.9698)

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)

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 00:02:04, output 00:02:04, 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

15 packets input, 3423 bytes, 0 no buffer

Received 14 broadcasts (0 multicast)

0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 13 multicast, 0 pause input

0 input packets with dribble condition detected

18 packets output, 5100 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

I hope that is the configuration information you wanted.

Thanks,

Michael

barnmichael · ‎09-17-2012

Pardon my dyslexia, the neighboring switch is a 3560.

Michael

Peter Paluch · ‎09-17-2012

Hello Michael,

3750 error:

Port Name Status Reason

Gi1/0/8 err-disabled bpduguard

This tells you that the ports was disabled because of the BPDU Guard configured either globally or on the port. Did you configure that intentionally?

It would be best to post the configuration of the 3750 switch, or at least the configuration of the port Gi1/0/8.

Best regards,

Peter

barnmichael · ‎09-17-2012

srn-enco-sw#sho int gig 1/0/8

GigabitEthernet1/0/8 is down, line protocol is down (err-disabled)

Hardware is Gigabit Ethernet, address is 001a.e2e8.4688 (bia 001a.e2e8.4688)

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)

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 00:52:32, output 00:52:33, 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

73409090 packets input, 1888626546 bytes, 0 no buffer

Received 12485 broadcasts (0 multicast)

0 runts, 0 giants, 0 throttles

1 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 2189 multicast, 0 pause input

0 input packets with dribble condition detected

312603116 packets output, 2297245927 bytes, 0 underruns

0 output errors, 769616 collisions, 7 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

Peter Paluch · ‎09-17-2012

Michael,

The configuration I am looking for is the output of the command

show running-config interface gi1/0/8

Thank you!

Best regards,

Peter

barnmichael · ‎09-17-2012

srn-enco-sw#show running-config interface gi1/0/8

Building configuration...

Current configuration : 335 bytes

!

interface GigabitEthernet1/0/8

switchport access vlan 7

switchport mode access

switchport port-security

switchport port-security aging time 2

switchport port-security violation restrict

switchport port-security aging type inactivity

macro description cisco-desktop

spanning-tree portfast

spanning-tree bpduguard enable

end

Peter Paluch · ‎09-17-2012

Michael,

The Gi1/0/8 port is currently configured for attachment of a single PC, and is specifically configured to prevent another switch from being attached.

My recommendation is to configure this port, and also the port on the 3560, as a trunk port, then create appropriate VLANs on the 3560 and assign the required ports on the 3560 to required VLANs.

The 3750 should be configured as follows (you may paste the following lines directly to the global configuration mode entered by the configure terminal command):

default interface gi1/0/8

interface gi1/0/8

switchport trunk encapsulation dot1q

switchport mode trunk

end

The port on the 3560 should be configured in an identical way, just the port name should be changed to gi0/24.

Are you familiar with creating VLANs and assigning access ports into them?

Best regards,

Peter

barnmichael · ‎09-18-2012

OK, I've got the two switches working together per your instructions. I'm not sure if the VLANS are set up right but everything is talking to each other as they should. I'm using VLAN 7.

Thanks for your help,

Michael