Keepalives are sent on the Catalyst 2940, 2950, 2950-LRE, 2955, 2970, 3550, 3560 or 3750 switch to prevent loops in the network. The primary reason for the keepalives is to prevent loops as a result of Type 2 cabling. Keepalives are sent on ALL interfaces by default in 12.1EA based software. Starting in 12.2SE based releases, keepalives are NO longer sent by default on fiber and uplink interfaces.

If we want to achieve the same situation under the 2950 we need to enter the "no keepalive" command in the interface.