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3550-12T problems

We just installed a new 3550-12T with the EMI image at a client location. THe routing aspect is fine, unfortunately anything plugged into this switch is having all sorts of layer two problems. We are dropping packets from servers plugged into it and from switches plugged into it. It seems that it is only negotiating half duplex on all of the interfaces. Do these ports have to be hard coded if they are not being plugged into gig interfaces? I have seen a similar occurance on the 4507, except on that you wont even get a link unless you hard code speed and duplex.


Re: 3550-12T problems

In the case of 3550-12T, the IEEE 802.3AB autonegotiation protocol manages the switch settings for speed (10 Mbps, 100 Mbps, and 1000 Mbps excluding GBIC ports) and duplex (half or full). There are situations when this protocol can incorrectly align these settings, reducing performance.

A mismatch occurs under these circumstances:

a)A manually-set speed or duplex parameter is different from the manually set speed or duplex parameter on the connected port.

b)A port is set to autonegotiate, and the connected port is set to full duplex with no autonegotiation.

To maximize switch performance and ensure a link, follow one of these guidelines when changing the settings for duplex and speed:

a)Let both ports autonegotiate both speed and duplex.

b)Manually set the speed and duplex parameters for the ports on both ends of the connection.

If a remote device does not autonegotiate, configure the duplex settings on the two ports to match.

The speed parameter can adjust itself even if the connected port does not autonegotiate.

The following URL might be useful to you.


Re: 3550-12T problems

100 half is common when negotiation fails, often because the hosts are hard configured. When the switch is running half and the host full the switch will drop a lot of packets.

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