SFP Connections between WS-C2960G-48TC-L and WS-C2960S-24TS-L

[Chuan Liu]

Hi,

I have 2 SPF modules in place in each of the above 2 switches that are located in different buildings. I can have only one link UP. Are there license requirements on this?

The configurations are as follows:

The 2 interfaces in 2960G

-------------------

switchport mode trunk
switchport mode trunk
media-type sfp
channel-group 6 mode active

The 2 interfaces in 2960S

--------------------

switchport mode trunk
switchport mode trunk
channel-group 6 mode active

Show interface statu shows the SFP are recognized, but the no fiber is dectected on one port. No LED light is seen on this physical port, not even orange.

--------------2960S

Gi1/0/25  connected    trunk      a-full a-1000 1000BaseLX SFP
Gi1/0/26  notconnect   1            auto   auto 1000BaseLX SFP

--------------2960G

Gi0/46           notconnect   1            auto   auto 1000BaseLX SFP
Gi0/47           connected    trunk      a-full a-1000 1000BaseLX SFP

The strange thing to me is that when I take off the working fiber, the other one comes up. That is to say, only one link can be working at a time.

This at least elimiates the fiber cable issues, or any SFP module faults. This leads me to think of the license issue. But....

I have the third switch, a WS-C2960S-48TS-L, and 4 more modules are installed

[Reza Sharifi]

Hi

This is not a license issue.

What happens if you delete the PortChannel?

I also see that the 2 ports that are working are a full 1000 mode while the other 2 are in auto mode.

can you change the auto to full 1000 and test again?

HTH

Reza

[Chuan Liu]

Hi Reza,

Thanks for the quick response.

These SFP  port speed is not configurable. I can only put ' speed nonegotiate', but no luck.

Regards.

Larry

[Leo Laohoo]

On the port channel, enter the command "switport nonegotiate".

[Chuan Liu]

Hi,

Still no luck.

These are layer 2 commands. But the layer 1 is 'notconnected'.

I cannot remove ether-channel as some MAC hosts only work with spanning-tree disabled.

This might be the thing I need to try next. This is in a production network. I will schedule time to enable the spanning-tree and try removing ether-channel.

Thanks.

Larry

[Reza Sharifi]

Hi Larry,

Let us know if that fixes the issue.

May be we can help some one else in the future with the same issue

Thanks,

Reza

[Reza Sharifi]

Hi Larry,

Do you have the same issue if you don't put the ports in an Etherchannel?

Reza

[Chuan Liu]

Hi,

I have some updates.

1. C2960G is using IOS 12.2(55)SE while C2960S is using 12.2(53)SE2.

2. I connected the 2960G with another 2960S via 2 Cat5e cables, and they worked fine both in Etherchannel and non-channel.

3. I defaulted the one SFP port on each end, and tried both trunk and access port configurations on this link, the 2690G side did not come up but the 2960S side showed 'UP'. There is communication between them though, as when I 'shutdown' 2960G end, 2960S port shows 'notconnected'; when I 'no shut', 2960S shows 'connected'.

So to summarize, on the two pairs of SFP ports between one C2960G and one C2960S, only one link can be 'UP' on C2960G side. On the C2960S side, both links show 'UP', but no traffic comes into the port that connects to the 'notconnect' port of C2960G, only output numbers increase.

What else can I try?

Regards.

Larry