cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
4125
Views
0
Helpful
40
Replies

Unable to connect to Core Switch

Abayomi Smith
Level 1
Level 1

Hello All,

I have a problem with extending the LAN on a client site . They are looking to extend the LAN with a 2960S-series switch. Already in place is a 4510 switch which the 2960 is connected to via fibre. The 2 switches are both set up but there is no connectivity as I cant ping between them or anything.

The management VLAN on the 2960 shows line up, protocol down, which I believe means the VLAN is enabled but there is a form of physical mismtach on the ports. I have attached the configs of both switches. I would appreciate if anyone can take a look and help out with what might be wrong. I feel it might be a problem with GBIC module compatibility. The SFP installed on both ends of the switch are GLC-SX-MMD. On the 4510, the SFP sits in a twingig converter (CVR-X2-SFP) but there is no light on it at all when the cables are plugged in.

I need to be sure its not a configuration issue. 

40 Replies 40

I have replicated the configuration in the lab with a 2950 as the access switch and a 3750 as a core switch and it works fine. This points to me that the config is ok (i stand corrected) and it must be something to do with physical connection. (maybe twin gig converters on core switch). My fear is splashing out on another twin gig converters as I initially thought it was a problem with SFP's got new ones and swapped them and it turned out it wasn't.

If your not getting link lights, its a layer 1 issue (if the ints are not shut).  What type of fiber are you using and sfps?

Have you tried rolling the fiber at one end?  Moving the tx and rx on one side.

Hi Jimmy, the SFP's are GLC-SX-MM, initially used GLC-SX-MMD, however checked a Cisco doc that didn't list the SFP as compatible with a twin gig converter(X2) so got the former as a replacement. Swapped cables and all but nothing.

Sent from Cisco Technical Support iPhone App

Not swapping the cables, but rolling the fiber, there is a difference.

Are they directly connected or go through a patch panel?

They go through a fibre patch panel but I have actually connected the devices directly eliminating the Fibre patch panel and still no connection.

Sent from Cisco Technical Support iPhone App

Ok, someone else will have to take the helm here as its Saturday morning and I am heading out to take the woman for her errands. They use the LC type connector and they were directly connected using the same cable, its not a rolling issue (or I have never seen this, normally that cable is rolled already.  The cool thing about problems like this is learn so much along the way!  I wish you luck.

Are you using a single mode or multi mode fiber patches?

Hi Dragos,

Its Mulitmode.

I will get new cables and try again on monday just in case.. The cables are LC-LC i believe. Will check and confirm.

Thank you so much for your help Dragos and Jimmy, its really appreciated. I am not that versed in fibre cabling but will get someone who is to help check.

Hi folks,

Just wanted to let you know the issue has been resolved by issuing

Switch(config)# hw-module module m port-group p

select gigabitethernet

this makes the supervisor engine use the gigabit Ethernet (if chosen) instead of the ten gigabit port.

Stumbled on this while going through some Cisco documentation. Also had to configure int gig5/3 & 4 instead of int tengig5/1( as configured original, see posted config)

Many thanks to Dragos, janko and jimmy. I appreciate your help.

Sent from Cisco Technical Support iPhone App

Sent from Cisco Technical Support iPhone App

Hy Abayomi,

Thanks for  the solution. i was really curious about the problem.

Best regards,

Dragos Tudor

Glad to hear, admittedly I would not of got the solution you arrived at, congrats and nice job!!  Thanks for the update, I will file that solution away in the memory banks!

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: