Mô tả máy tính sẽ gửi một thông báo lỗi Destination Unreachable cho các khách hàng cố gắng để gửi các gói dữ liệu thông qua máy tính với một mạng từ xa đó có tuyến đường. Cung cấp thông tin cho các bộ định tuyến về tốc độ dữ liệu nhận được, | Lesson 5 Configuring Windows Firewall 15-55 Table 15-5 ICMP Options ICMP Option Description Allow Outgoing Destination Unreachable The computer sends a Destination Unreachable error message to clients who attempt to send packets through the computer to a remote network for which there is no route. Allow Outgoing Source Quench Offers information to routers about the rate at which data is received tells routers to slow down if too much data is being sent and it cannot be received fast enough to keep up. Allow Outgoing Parameter Problem The computer sends a Bad Header error message when the computer discards data it has received that has a problematic header. This message allows the sender to understand that the host exists but that there were unknown problems with the message itself. Allow Outgoing Time Exceeded The computer sends the sender a Time Expired message when the computer must discard messages because the messages timed out. Allow Redirect Data that is sent from this computer will be rerouted if the path changes. Security Alert Generally you should enable ICMP exceptions only when you need them for troubleshooting and then disable them after you have completed troubleshooting. Make sure that you do not allow or enable these options without a full understanding of them and of the consequences and risks involved. How to Enable ICMP Exceptions To enable a global ICMP exception for all connections on a computer use these steps 1. Click Start and then click Control Panel. 2. In the Control Panel window click Network And Internet Connections. 3. In the Network And Internet Connections window click Windows Firewall. 4. In the Windows Firewall dialog box click the Advanced tab. 5. In the ICMP section click Settings. 6. Select the check box for the exception you want to enable. 7. Click OK to close the ICMP Settings dialog box. Click OK again to close the Windows Firewall dialog box. 15-56 Chapter 15 Configuring Network and Internet Connections To enable an ICMP .
