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Cisco 2950 Switch replacement problem

budman007
Level 1
Level 1

I have a Cisco 2950 switch with a dead fan in it. I am replacing with another Cisco 2950 switch. Both are 24 port switches. The difference is, the old switch has built in Gigabit fibre ports(25&26), that fibre goes from the fibre box directly into the switch using a SC to ST fibre patch cable. The new switch has Gigabit fibre ports(25&26), but it requries the GBIC cards to plug the SC to SC fibre patch cable to work. My problem is this: When I plug the SC from he the Fibre box to the new GBIC Switch, I get no data light, period. I have tried swapping switches, gbic cards, sc-sc cables, etc. The output from the fibre box is good and working now, so I know the fibre isn't bad. I am using the same two fibre strands from the fibre box to the new switch, just with a sc-sc cable because a sc-st is now being used. What am I missing?

Thanks!           

19 Replies 19

devils_advocate
Level 7
Level 7

Try swapping the Fibre pairs over.

What I mean is, the fibre cable will have two single cables (red and black ended perhaps) so swap these over. An SC cable will probably have a little clip which comes apart and allows you to swap the cables over.

What is the structured cabling, multimode or single mode?

I swapped over and over on each end, still no lights. Multimode cabling. I can't fathom that there is some weird cabling difference inside the fibre box because of he switch differences. I am fairly sure I have the right pair in the fibre box, because when I unplug one, the current old switch, either port 25 or port 26 lights go out.

Attached in a picture inside the fibre box. Disregard the fibre with the blue connectors that are marked, i inked them before I traced the cables. The others are marked correctly, the Green and Red ink are port 25 and the Blue and Orange ink are port 26. I simply unplug them where they are inked and plug in the SC-SC connectors and go directly to the new switch, I tried in both ports on the new switch, different GBIC, etc.

could you post #show inventory with inserted sfp?

as well #show inter [your_port_number] capabilities,  #show run inter [your_port_number]

That isn't a command for his version of switch. The old switch doesnt have a Sfp. I took the config from the old switch and applied to the new switch, but edited the port names from FE(old switch) to GB(new switch), really, though you should get active lights or even amber lights with a blank config, just need connectivity. right?

Hi, Dale...

According to your description and this article:

http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a00800a7af7.shtml#cat2950

you have replaced this switch (p/n:WS-C2950SX-24) to this (p/n:WS-C2950G-24-EI)... Right?

Are you use the right GBIC - 1000BASE-SX, p/n:WS-G5484?

Could you post output of #show interface to ensure that the switch recognizes the GBIC and displays the correct media type?

devils_advocate
Level 7
Level 7

What is the model number of the new GBIC you have installed? It should be written on it.

Can you provide a show run of the interface?

I am thinking either a mismatch in the cable and GBIC types or autonegotiation is not working correctly.

Phillip Wilson
Level 1
Level 1

Try putting "no negotiate" on the fiber port. I have had this issue before and this helped.

Sent from Cisco Technical Support iPhone App

Thanks for the sugesstions, I will try some, here is more info.

The old switch is WS-C2955C-24. The new one is WS-C2950G-24-EI.

Here is a pic. It's the GBIC card, which I tried today to take out a working gbic from another switch and tested it, still no lights....So I am 99% the gbic isnt the problem. 

devils_advocate
Level 7
Level 7

1000base-lx is for single mode fibre, you said earlier yours is multimode.....

1000base-sx is for multimode

Phillip Wilson
Level 1
Level 1

The LX GBIC will work for MMF and also SMF. 10km distance for Single mode. 550m for Multi Mode. See link below.
http://www.cisco.com/en/US/prod/collateral/modules/ps5455/ps6577/product_data_sheet09186a008014cb5e_ps872_Products_Data_Sheet.html


Sent from Cisco Technical Support iPhone App

Here is the config from the new Switch.

b6m01csb827#sh ru
Building configuration...

Current configuration : 3961 bytes
!
version 12.1
no service pad
service timestamps debug datetime localtime show-timezone
service timestamps log datetime localtime show-timezone
no service password-encryption
service sequence-numbers
!
hostname b6m01csb827
!
enable secret 5 $1$IS.v$X683bFbcJufwB6EOGbZ0t/
enable password cisco
!
clock timezone cst -6
clock summer-time cdt recurring
ip subnet-zero
!
!
!
spanning-tree mode pvst
no spanning-tree optimize bpdu transmission
spanning-tree extend system-id
no spanning-tree vlan 1
!
!
!
!
interface FastEthernet0/1
switchport mode access
switchport voice vlan 99
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/2
switchport access vlan 40
switchport mode access
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/3
switchport access vlan 50
switchport mode access
switchport voice vlan 99
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/4
switchport access vlan 10
switchport mode access
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/5
switchport access vlan 10
switchport mode access
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/6
switchport access vlan 50
switchport mode access
switchport voice vlan 99
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/7
switchport access vlan 10
switchport mode access
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/8
switchport access vlan 10
switchport mode access
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/9
switchport access vlan 80
switchport mode access
speed 10
duplex half
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/10
switchport access vlan 50
switchport mode access
duplex half
no cdp enable
!
interface FastEthernet0/11
switchport access vlan 290
switchport mode access
duplex half
no cdp enable
!
interface FastEthernet0/12
switchport access vlan 50
switchport mode access
duplex half
no cdp enable
!
interface FastEthernet0/13
switchport access vlan 10
switchport mode access
duplex half
no cdp enable
!
interface FastEthernet0/14
switchport access vlan 50
switchport mode access
duplex half
no cdp enable
!
interface FastEthernet0/15
switchport access vlan 10
switchport mode access
duplex half
no cdp enable
!
interface FastEthernet0/16
switchport access vlan 50
switchport mode access
duplex half
no cdp enable
!
interface FastEthernet0/17
switchport access vlan 50
switchport mode access
duplex half
no cdp enable
!
interface FastEthernet0/18
switchport access vlan 10
switchport mode access
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/19
switchport access vlan 50
switchport mode access
speed 100
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/20
switchport access vlan 10
switchport mode access
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/21
switchport access vlan 10
switchport mode access
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/22
switchport access vlan 10
switchport mode access
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/23
switchport access vlan 10
switchport mode access
no cdp enable
spanning-tree portfast
!
interface FastEthernet0/24
switchport access vlan 50
switchport mode access
switchport voice vlan 99
no cdp enable
spanning-tree portfast
!
interface GigabitEthernet0/1
switchport mode trunk
!
interface GigabitEthernet0/2
switchport mode trunk
!
interface Vlan1
no ip address
no ip route-cache
shutdown
!
interface Vlan60
ip address 10.10.241.48 255.255.255.0
no ip route-cache
!
ip default-gateway 10.10.241.1
ip http server
snmp-server community public RO
snmp-server enable traps snmp authentication
snmp-server host 10.10.240.46 public  snmp
!
line con 0
exec-timeout 0 0
line vty 0 4
password cisco
login
line vty 5 15
password cisco
login
!
ntp clock-period 17179796
ntp server 10.10.240.2 key 0 prefer
!
end

b6m01csb827#show inventory
NAME: "b6m01csb827", DESCR: "Cisco Catalyst c2950 switch with 24 10/100 BaseTX ports and 2
GBIC (Gigabit Interface Converter) slots"
PID: WS-C2950G-24-EI   , VID:    , SN: FHK0713Y0DM

NAME: "GigabitEthernet0/1", DESCR: "longwave fiber gigabit ethernet port adapter"
PID: GBIC_LX           , VID: 30 30 30 30, SN: 0209110442301672

NAME: "GigabitEthernet0/2", DESCR: "longwave fiber gigabit ethernet port adapter"
PID: GBIC_LX           , VID: 30 30 30 30, SN: 0209110501167948

Phillip Wilson
Level 1
Level 1

I would try putting the " switchport nonegotiate" on Interface on both sides of the fiber first. Then I would check your distance. Are you past 550m for MMF? Do you have SMF available to test?


"switchport nonegotiate" says: "Do not send or respond to DTP from this end. Disable all DTP on this port." Best used on user access ports, when trunking to non-Cisco switches, when trunking to a router, or if you are paranoid about fast convergence.

Sent from Cisco Technical Support iPhone App

If the config needed changed, wouldnt that mean that when I plugged this switch into another switch using the same gbic cards and cables that it wouldnt have lit up? One thing I did notice is the current cable in place that runs from the fiber box to the old switch(SC to ST) is a lot thinner then my new cable to the new switch(SC to SC). I have been told we have both Multi and Single mode in our enviroment, how can I tell which this is? I couldnt find anything stamped on the fiber that runs to the fiber box.

Did you check the device this 2950 is connected to?

Fe fiber ports use different wavelength light then ge sfp's!

? 100BASE-LX (LC connectors @ 1,300 nm):
1000base:
850 nm, 1310 nm and 1550 nm wavelenghts


Sent from Cisco Technical Support iPad App

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