2960-S SFP Configuration

Answered Question
Aug 13th, 2010
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Hi,

first up I'm a beginner with cisco devices! We recieved out 1st Cisco 2960's today and began to setup the device using the express setup. Input all correct IP/Subnet/Gateway/pwd etc and all went ok. We then connected two 2960's via OM3 and the SFP's that were ordered with the units. Connected them up and I have connectivity between the two through the SFP (green lights on both ends). One of the switches has an uplink from a 3com 4200G via cat5, we tested the connectivity to the network on this switch and it is doing its job. However, the switch which is connected solely via the SFP is not communicating. On the 3Coms the SFP port is shutdown by default and it needs to be enabled. Is there a similar problem occuring here? What are the commands for correctly configuring the SFP ports on both switches, bearing in mind they are on the same vlan 1 (default).


Any help is greatly appreciated!


Matt

Correct Answer by Conor Cunningham about 6 years 9 months ago

Hi Matt,


At first glance I can't see anything wrong (I did stay up rather late last

night so I'm not at my best today). So, I would recommend applying the

following configuration under the interfaces that are connected to each

other by the fibre


interface gig1/0/x - where x is your trunk connection

switchport trunk encapsulation dot1q

switchport mode trunk

switchport nonegotiate


This way we can be sure that the trunk is set, although it should have

happened automatically.


After that, on both switches, do a 'show ip interface brief' and ensure that

the link is up for the interfaces in question.


Then do a ping to from each switch to the other.


Let me know how you get along.


Cheers,


Conor




On 15 August 2010 06:20, murraybridgehs

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Conor Cunningham Fri, 08/13/2010 - 04:20
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Hi Matt,


Can you show us your config the for the sfp ports


i.e. show running interface gig0/xx


and also, can you show the output of the command


show ip interface brief


Cheers,


Conor

murraybridgehs Fri, 08/13/2010 - 20:47
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Hi Conor,


Cheers for the quick reply!


I have attached the output from each switch.


Building 1 is the Cisco 2960-S with the uplink from the 3Com


Building 2 is also a 2960-S connected to Building 1 purely through the SFP ....which isnt relaying the traffic.


If you could step me through the commands that would be awesome!


Cheers,


Matt

Conor Cunningham Sat, 08/14/2010 - 02:21
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Hi Matt,


Do you think you can draw a picture of sorts depicting what is connected to what and via which interfaces? I'm a bit confused by your original post.


Cheers,


Conor

Conor Cunningham Sat, 08/14/2010 - 04:22
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Matt,


Good pic. Cheers. The problem is most likely the link between the two switches. By default, they should have formed a trunk link and from the output of the show ip interface brief command, you can see that both interfaces are up.


If you could post the running config of both switches, that would be great. Be sure to remove any sensitive configuration - passwords etc.


Cheers,


Conor

murraybridgehs Sat, 08/14/2010 - 05:36
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Conor,

whats the command(s) to display the running config from the prompt?


Cheers,

Matt

Conor Cunningham Sat, 08/14/2010 - 07:01
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Matt,


'show running-config' will show the running config. 'show startup-config'

will show the config that is saved to nvram.


After making changes, be sure to execute 'wr mem' to save the running conf

to the startup conf.


You can also copy the running or startup config to tftp. For example, 'copy

running-config tftp://10.x.x.x'


Cheers,


Conor

murraybridgehs Sat, 08/14/2010 - 21:19
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Hi Conor,


I have attached the requested configs of both switches.


You will notice that on the config of the Building 1 switch, there are approx 28 PC's already attached to this switch.


The SFPs are on port 49 on both switches.


Cheers!


Matt

Correct Answer
Conor Cunningham Sun, 08/15/2010 - 08:53
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Hi Matt,


At first glance I can't see anything wrong (I did stay up rather late last

night so I'm not at my best today). So, I would recommend applying the

following configuration under the interfaces that are connected to each

other by the fibre


interface gig1/0/x - where x is your trunk connection

switchport trunk encapsulation dot1q

switchport mode trunk

switchport nonegotiate


This way we can be sure that the trunk is set, although it should have

happened automatically.


After that, on both switches, do a 'show ip interface brief' and ensure that

the link is up for the interfaces in question.


Then do a ping to from each switch to the other.


Let me know how you get along.


Cheers,


Conor




On 15 August 2010 06:20, murraybridgehs

murraybridgehs Mon, 08/16/2010 - 03:43
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Hi Conor,   Turns out i misinformed you re building 1 switch. It is NOT aquiring ip addressing from the 3com at all. Turns out 10 of the workstations i was basing my assumption on were connected to the cisco and the others were on another 3com! And of course i only saw the stations connected to the 3com and assumed it was connected to the cisco :/  I troubleshooted the 3com and cisco switch.... I have green lights on both....the uplink port is a trunk port on both....everything SHOULD be A OK.... But its not.....no go....  Seems our network has more serious issues with our 3com core vlan switch. From an engineer i was talking to today said our core VLAN switch is having tree-spanning issues. All the subsequent switches added to the network are not pointing to the VLAN switch causing us headaches.  So thats it in a nutshell...its been a long day and 3hours on my iphone!!  So seeing this is a cisco forum... I think the support will stop here! I will have to rectify the 3com issues.  I really appreciate your help conor and youve taught me some valuable information! So thats something!  Thanks again!  Matt

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