I'm currently having a 4510R running IOS and 2x 6006 running CatOS. I had trunk the Gi1/3 & Gi2/3 of the 4510R to the 1st 6006 mod 3 & mod 4 and the Gi1/4 and Gi2/4 of the 4510R to the 2nd 6006 mod 3 & mod 4. Gi1/3 & Gi2/3 are in port channel 1 and Gi1/4 & Gi2/4 are in port channel 2. configurations on all switches for etherchannel are set to desirable. After configurations, only the Gi1/3 show protocol down (not connected) whereby all other 3 protocols are up. Few minutes later, an error msg shown : "%C4K_HWPORTMAN-4-BLOCKEDTXQUEUE: Blocked transmit queue HwTxQId1 on Switch Phyport Gi1/3, count=81". But i was still able to ping my other switches.
Hope that there will be someone to alighten me on how to overcome the error msg and the down protocol on the Gi1/3 on the 4510R.
From Cisco doc on 4500 error messages:_
%C4K_HWPORTMAN-4-BLOCKEDTXQUEUE:Blocked transmit queue HwTxQId[dec]on [char], count=[dec]
The switch generates %C4K_HWPORTMAN-4-BLOCKEDTXQUEUE:Blocked transmit queue HwTxQId[dec]on[char], count=[dec] errors.
This rate-limited message indicates that a transmit queue on a port is blocked for reasons other than ?paused?. In other words, the traffic on that port is being limited and blocked. You see the blocked transmit queue messages if the Supervisor Engine is not able to send packets to the line card because of the reception of a busy bit from the line card. Bad hardware or a speed/duplex mismatch can cause this problem. The workaround is to configure both sides of the link to autonegotiate for speed and duplex. Issue the shut/no shut command in order to recover the port. If the problem persists, move the connected device to another port and see if the problem happens there. As a final measure to unblock the transmit (Tx) queue, issue the hw-module reset command in order to reboot the switch or reset the line card.
Check the speed duplex setting. If all okay then try a different port on the 4510R. If still doesn't work try different connectors and if possible a different fibre.