02-22-2007 07:12 AM - edited 03-05-2019 02:30 PM
I have two Catalyst 2950 switches that I am trying to link together, but when I run a cable between the two (doesn't matter which port)it produces a wierd fast flashing light on the ports and stops all traffic on the switches. As soon as I remove the cable, traffic resumes as normal. Any ideas?
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02-27-2007 09:37 AM
no spanning-tree vlan 1 <--- This is the issue. No spanning tree and two connections between switches equals a network loop. Unplug one cable, enable spanning tree and plug the second cable back in. If you do a sh spanning-tree, one of the ports will be forwarding and one of the ports will be blocking. This is spanning-tree in action (stopping that network loop). Delete the etherchannel configuration on port 22 and re-configure it for ports 23 and 24. Spanning-tree no longer needs block any ports, becasue they are now one logical port.
02-22-2007 07:51 AM
Are both switches connected to upstream devices in addition to their sw-sw connections?
Can you get a show port, or equivalent command to see what status the ports are showing?
Might their be a spanning tree loop when you interconnect the switches?
Are you using a cross-over cable to connect the switches?
02-22-2007 01:40 PM
Switch 1 is acting as the VTP server and is connected to the network gateway (port 1). Switch 2 is the VTP client and needs to connect to switch 1 so that is can connect to the outside world. I can view the status of the ports and they are both listed as "Down". I'm not a pro at this yet, so I'm not sure what a spanning loop is. I do not have any spanning-tree configured for either switch. The cable I am using to connect them is a regualr cable...not crossover.
02-22-2007 08:33 AM
Please post configs from both switches.
02-22-2007 01:42 PM
Which config do you need. Port config ,or switch? Here are the ports:
Rack1Switch1#sho int fa0/23
FastEthernet0/23 is down, line protocol is down (notconnect)
Hardware is Fast Ethernet, address is 0014.1cb3.ae57 (bia 0014.1cb3.ae57)
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, 100Mb/s, media type is 100BaseTX
input flow-control is unsupported output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 18:58:42, output 18:58:42, 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
685119 packets input, 44076711 bytes, 33 no buffer
Received 676443 broadcasts (0 multicast)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 33 ignored
0 watchdog, 18 multicast, 0 pause input
0 input packets with dribble condition detected
933551 packets output, 59750754 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
Rack1Switch2#sho int fa0/23
FastEthernet0/23 is down, line protocol is down (notconnect)
Hardware is Fast Ethernet, address is 0013.c304.0197 (bia 0013.c304.0197)
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, 100Mb/s, media type is 100BaseTX
input flow-control is unsupported output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 19:12:11, output 19:12:12, 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
933539 packets input, 59750315 bytes, 34 no buffer
Received 920942 broadcasts (0 multicast)
0 runts, 0 giants, 0 throttles
2 input errors, 1 CRC, 1 frame, 0 overrun, 34 ignored
0 watchdog, 19 multicast, 0 pause input
0 input packets with dribble condition detected
685129 packets output, 44077250 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
02-22-2007 01:46 PM
02-22-2007 01:48 PM
STP has been disabled for both switches.
02-22-2007 01:53 PM
What had happened is this. I had two lines running between switches and both were configured in an etherchannel. I was using ports 23 and 24. I logged in remotely last week and needed to make some changes, so I deleted the Etherchannel from switch 2 and it locked up everything. I got the local tech on the phone and walked him thru some steps. 1. We moved the cable in port 23 over to port 22, but the problem remained. Then, when we removed the cable from port 24 (leaving only one cable connected), everything returned to normal. Now, if I plug that cable back into port 24 (or 23), it locks up the switches until I remove it. I have since created an etherchannel on port 22 of sw1 and sw2, but can't add another line to that wihtout locking up the switches.
02-22-2007 02:21 PM
Post both switch configs please. I would never turn off STP , it is not causing your problems , if you are using pagp or lacp to create the channels and they are not correct it will disable the link , this is just telling you what you configured is not correct . If you are just trying to create a nontrunk etherchannel it should be as simple as putting the following on each of your interfaces " channel-group 1 mode desirable non-silent" . If it is a trunk there is more configuration needed under the port channel interface .
Configure this before applying to the interfaces . The speed and duplex for all ports must be the same and i would make sure the native vlan is the same across all 4 interfaces.
Interface port-channel 1
switchport mode dynamic desirable
02-22-2007 02:41 PM
Switch 1:
User Access Verification
Password:
Rack1Switch1>enable
Password:
Rack1Switch1#sho running-config
Building configuration...
Current configuration : 1832 bytes
!
version 12.1
no service pad
service timestamps debug uptime
service timestamps log datetime
service password-encryption
service sequence-numbers
!
hostname Rack1Switch1
!
enable secret ****
!
clock summer-time UTC recurring last Sun Mar 1:00 last Sun Oct 2:00
ip subnet-zero
!
ip host Rack1Switch2 10.4.167.91
ip host Rack1Switch3 10.4.167.92
ip domain-name westernmotorcom
ip name-server 10.4.167.100
!
!
spanning-tree mode pvst
no spanning-tree optimize bpdu transmission
spanning-tree extend system-id
no spanning-tree vlan 1
!
!
!
!
interface Port-channel1
switchport mode trunk
flowcontrol send off
!
interface FastEthernet0/1
!
interface FastEthernet0/2
!
interface FastEthernet0/3
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
duplex half
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
!
interface FastEthernet0/21
!
interface FastEthernet0/22
switchport mode trunk
channel-group 1 mode active
!
interface FastEthernet0/23
switchport mode trunk
!
interface FastEthernet0/24
switchport mode trunk
!
interface Vlan1
ip address 10.4.167.90 255.255.255.0
no ip route-cache
!
ip default-gateway 10.4.167.253
ip http server
snmp-server community Public/RO RO
snmp-server community Public RO
snmp-server community Private RW
!
line con 0
password ***
login
line vty 0 4
password ***
login
line vty 5 15
password ***
login
!
!
end
02-22-2007 02:54 PM
Switch 2:
Password:
Rack1Switch2>enable
Password:
Rack1Switch2#sho running-config
Building configuration...
Current configuration : 1869 bytes
!
! Last configuration change at 16:35:11 UTC Thu Feb 22 2007
!
version 12.1
no service pad
service timestamps debug uptime
service timestamps log datetime
service password-encryption
service sequence-numbers
!
hostname Rack1Switch2
!
enable secret ****
!
clock summer-time UTC recurring last Sun Mar 1:00 last Sun Oct 2:00
ip subnet-zero
!
ip host Rack1Switch1 10.4.167.90
ip host Rack1Switch3 10.4.167.92
ip domain-name westernmotorcom
ip name-server 10.4.167.100
!
!
spanning-tree mode pvst
no spanning-tree optimize bpdu transmission
spanning-tree extend system-id
no spanning-tree vlan 1
!
!
!
!
interface Port-channel1
switchport mode trunk
flowcontrol send off
!
interface FastEthernet0/1
!
interface FastEthernet0/2
!
interface FastEthernet0/3
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
switchport mode trunk
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
!
interface FastEthernet0/21
!
interface FastEthernet0/22
switchport mode trunk
channel-group 1 mode active
!
interface FastEthernet0/23
switchport mode trunk
!
interface FastEthernet0/24
switchport mode trunk
!
interface Vlan1
ip address 10.4.167.91 255.255.255.0
no ip route-cache
!
ip default-gateway 10.4.167.253
ip http server
snmp-server community Public/RO RO
snmp-server community Public RO
snmp-server community Private RW
!
line con 0
password ***
login
line vty 0 4
password ***
login
line vty 5 15
password ***
login
!
!
end
02-24-2007 11:33 PM
why are you configuring Etherchannel? Looking at your config file you have only 1 interface configured in the Etherchannel. Etherchannel is to increase bandwidth by combining multiple interfaces to act as one.
interface Port-channel10
description *****
switchport
interface GigabitEthernet5/5
switchport access vlan 110
channel-group 10 mode on
interface GigabitEthernet5/6
switchport access vlan 110
channel-group 10 mode on
02-26-2007 06:01 AM
That's the whole point. I am trying to set up an Etherchannel using 2 ports, but when I connect the second cable (0/24 of SW1 to 0/24 of SW2), it stops all activity on the switch. There is currently one cable connecting the switches, but in order to utilize an Ethercahnnel, I need 2 or more connected.
02-26-2007 06:08 AM
That's the whole point. I am trying to set up an Etherchannel using 2 ports, but when I connect the second cable (0/24 of SW1 to 0/24 of SW2), it stops all activity on the switch. There is currently one cable connecting the switches, but in order to utilize an Ethercahnnel, I need 2 or more connected.
02-26-2007 07:17 AM
You either disable STP for all VLANs or you enable it for all of them.
Etherchannel requires the same setting for the agregated ports/links.
Also I believe that the switchport mode trunk is redundant there. You either configure it at port level or at etherchannel level.
Make the two ports explicitly members of the channel group you defined above.
Do these things on both switches.
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