If a layer 2 switch (such as the 2950) is only needed for external connectivity and has no control plane exposure or special access into your interior network, it can function with quite adequate security for the network edge.
You should have security controls both upstream and downstream of it that perform the significant edge security functions. Generally an external-only switch does not need to do anything security-wise other than protect itself from security-related attacks. Without a control plane exposure (i.e. no publicly addressable interface, no snmp services etc.) it can do a decent job at that.
