D-Link DGS-3612G Product Manual - Page 158

From/To External Cost (0=Auto) Hello Time Migrate Edge P2P State LBD BPDU Restricted Role Restriced TCN xStack® DGS-3600 Series Layer 3 Managed Gigabit Ethernet Switch A consecutive group of ports may be configured starting with the selected port. This defines a metric that indicates the relative cost of forwarding packets to the specified port list. Port cost can be set automatically or as a metric value. The default value is 0 (auto). 0 (auto) - Setting 0 for the external cost will automatically set the speed for forwarding packets to the specified port(s) in the list for optimal efficiency. Default port cost: 100Mbps port = 200000. Gigabit port = 20000. value 1-200000000 - Define a value between 1 and 200000000 to determine the external cost. The lower the number, the greater the probability the port will be chosen to forward packets. The time interval between transmissions of configuration messages by the designated port, to other devices on the bridged LAN. The user may choose a time between 1 and 10 seconds. The default is 2 seconds. This field is only operable when the Switch is enabled for MSTP. When operating in RSTP mode, selecting yes forces the port that has been selected to transmit RSTP BPDUs. Choosing the True parameter designates the port as an edge port. Edge ports cannot create loops, however an edge port can lose edge port status if a topology change creates a potential for a loop. An edge port normally should not receive BPDU packets. If a BPDU packet is received, it automatically loses edge port status. Choosing the False parameter indicates that the port does not have edge port status. Choosing the True parameter indicates a point-to-point (P2P) shared link. P2P ports are similar to edge ports, however they are restricted in that a P2P port must operate in full duplex. Like edge ports, P2P ports transition to a forwarding state rapidly thus benefiting from RSTP. A P2P value of False indicates that the port cannot have P2P status. Auto allows the port to have P2P status whenever possible and operate as if the P2P status were true. If the port cannot maintain this status, (for example if the port is forced to half-duplex operation) the P2P status changes to operate as if the P2P value were False. The default setting for this parameter is True. This drop-down menu allows you to enable or disable STP for the selected group of ports. The default is Enabled. Use the pull-down menu to enable or disable the Loopback Detection function on the Switch for the ports configured above. For more information on this function, see the Loopback Detection field in the STP Bridge Global Settings window, mentioned earlier in this section. Choosing Enabled will allow the forwarding of BPDU packets in the specified ports from other network devices. This will go into effect only if STP is globally disabled AND Forwarding BPDU is globally enabled (See the STP Bridge Global Settings window above). The default setting Disabled, does not forward BPDU packets when STP is disabled. Toggle between True and False to set the restricted role state of the packet. If True causes the port not to be selected as the root port for the CIST or any MSTI, even if it has the best spanning tree priority vector, such a port will be selected as an Alternate Port after the Root Port has been selected. Setting this variable can cause lack of spanning tree connectivity. It is set by a network administrator to prevent bridges external to a core region of the network influencing the spanning tree active topology, possibly because those bridges are not under the full control of the administrator. This parameter is False by default. Toggle between True and False to set the restricted TCN of the packet. If True causes the port not to be selected as the root port for the CIST or any MSTI, even if it has the best spanning tree priority vector, such a port will be selected as an Alternate Port after the Root Port has been selected. Setting this variable can cause lack of spanning tree connectivity. It is set by a network administrator to prevent bridges external to a core region of the network influencing the spanning tree active topology, possibly because those bridges are not under the full control of the administrator. This parameter should be False by default. Click Apply to implement changes made. 142