mysterious 4500-x to 6500 fiber connection issue??

[baselzind]

im having a strange issue with a fiber connection between 4500-x and 6500 , it is a 10 gig connection with both LR sfb on both 4500 and 6500 and a sm cable , the issue is that the port on the 4500-x keep switching between connected and notconnected but the the port on the 6500 stays connected , when i check both interfaces on 4500 and 6500 it have gradually increasing crc errors and input errors on both switches , i tried replacing the cable , the sfb and the port with no avail , i tried switchport non-negotiate also tries setting it to trunk and access and still the same story , even when i connect the 4500-x with the same sfb to 2960-x sfb 10 gig as well there is no issues , also connecting the 2960-x to the 6500 shows no issues using the same 10 gig cable and sfb , please help as i ran out of solutions

[baselzind]

the port on the 4500 goes down "notconnected" for 1-3 seconds then it flips up again for also 1-3 seconds , i have noticed that when i try a new port the up and down start up initially longer like 4-5 minutes up then it starts and as the time passes and the issue starts , the duration keep decreasing until it reaches the 1-3 seconds period , once the issue starts even if remove the sfb+ and return it the up and down frequency stay the same it doesn't increase again like a fresh port. here is the sfb models

The 10 Gb SFP for 4500 is SFP-10G-LR

10 Gb SFP for 6509 is X2-10G-LR

[ttcroziercisco]

We are having the same issue with our 4500x's, which are connected by 10GB sfp to 4900's.  We have 2 4500x's and 2 4900's and did not have an issue for the 1st 8 months in production.  Then the issue started, the 4500x 10gb port will go down, but the 4900 will stay up.  We do not see errors on either side.  

 Once the issue started, it occurs every 5 hours.  Our 4500x's were replaced but the issue stayed the same.  We have replaced every possible hardware item, both 4500x's, the sfp's, the ports, the cables.  

When I change the trunk between the switches to 1 GB ethernet, the issue does not occur.  I even removed the layer 3 ip from the vlan which is allowed on the trunk, but that did not change anything.