HP Network Direr Software Products manual Prioritizing Network Traffic

662CHAPTER 15: PRIORITIZING NETWORK TRAFFIC

CAUTION: Many TCP and UDP based applications use dynamic port assignment to determine the TCP or UDP port that will be used as the source port. If your application definition contains a classifier for a TCP or UDP port that falls within a range that one or more of your devices may dynamically allocate to an application it could cause intermittent problems on your network. Whenever an application is dynamically allocated a port that is blocked it will be unable to function correctly.

CAUTION: Some applications allow the user to select the protocols and ports that are used. Whilst blocking the default protocol and port settings for this type of application will prevent an out-of-the-box instance from functioning correctly on your network, it cannot be guaranteed that this will block all instances of the application. Other instances may have been configured to use other protocols and ports.

Potential Hazards of The protocols SNMP, HTTP and Telnet are all used for network

Blocking SNMP, HTTP management purposes. 3Com Network Director uses SNMP to configure and Telnet its devices and, in some cases, can use HTTP and Telnet for device

discovery and configuration. HTTP and Telnet protocols are also used for manual configuration of devices. Blocking an application whose definition includes the ports used by these protocols would prevent 3Com Network Director from functioning correctly and prevent you from manually accessing these devices.

3Com Network Director will prevent you from blocking any application whose definition includes classifiers for the SNMP protocol unless you have first selected the PC that it is running on for prioritization. This is so that 3Com Network Director can continue to manage your network whilst SNMP is blocked.

By prioritizing the traffic of your network management PCs and by blocking SNMP you can prevent any unauthorized SNMP access on your network.