Chapter 12 Firewall Configuration
The following table describes the labels in this screen.
Table 70 Firewall: Anti Probing
LABEL | DESCRIPTION |
Respond to PING | The ZyXEL Device does not respond to any incoming Ping requests when |
on | Disable is selected. |
| Select LAN to reply to incoming LAN Ping requests. |
| Select WAN to reply to incoming WAN Ping requests. |
| Otherwise select LAN & WAN to reply to both incoming LAN and WAN Ping |
| requests. |
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Do Not Respond | Select this option to prevent hackers from finding the ZyXEL Device by probing for |
to Requests for | unused ports. If you select this option, the ZyXEL Device will not respond to port |
Unauthorized | request(s) for unused ports, thus leaving the unused ports and the ZyXEL Device |
Services. | unseen. By default this option is not selected and the ZyXEL Device will reply with |
| an ICMP Port Unreachable packet for a port probe on its unused UDP ports, and a |
| TCP Reset packet for a port probe on its unused TCP ports. |
| Note that the probing packets must first traverse the ZyXEL Device's firewall |
| mechanism before reaching this |
| mechanism blocks a probing packet, the ZyXEL Device reacts based on the |
| corresponding firewall policy to send a TCP reset packet for a blocked TCP |
| packet or an ICMP |
| drop the packets without sending a response packet. |
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Apply | Click Apply to save your changes to the ZyXEL Device. |
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Cancel | Click Cancel to begin configuring this screen afresh. |
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12.10 DoS Thresholds
For DoS attacks, the ZyXEL Device uses thresholds to determine when to drop sessions that do not become fully established. These thresholds apply globally to all sessions.
You can use the default threshold values, or you can change them to values more suitable to your security requirements.
Refer to Section 12.10.3 on page 191 to configure thresholds.
12.10.1 Threshold Values
Tune these parameters when something is not working and after you have checked the firewall counters. These default values should work fine for most small offices. Factors influencing choices for threshold values are:
•The maximum number of opened sessions.
•The minimum capacity of server backlog in your LAN network.
•The CPU power of servers in your LAN network.
•Network bandwidth.
•Type of traffic for certain servers.
If your network is slower than average for any of these factors (especially if you have servers that are slow or handle many tasks and are often busy), then the default values should be reduced.
You should make any changes to the threshold values before you continue configuring firewall rules.
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