Security 13-9

Src. Port: The source port to match. This is the port on the sending host that originated the packet.

D. Port: The destination port to match. This is the port on the receiving host for which the packet is intended.

On?: Displays Yes when the filter is in effect or No when it is not.

Fwd: Shows whether the filter forwards (Yes) a packet or discards (No) it when there’s a match.

Filtering example #1

Returning to our filtering rule example from above (see page 13-6), look at how a rule is translated into a filter. Start with the rule, then fill in the filter’s attributes:

1.The rule you want to implement as a filter is:

Block all Telnet attempts that originate from the remote host 199.211.211.17.

2.The host 199.211.211.17 is the source of the Telnet packets you want to block, while the destination address is any IP address. How these IP addresses are masked determines what the final match will be, although the mask is not displayed in the table that displays the filter sets (you set it when you create the filter). In fact, since the mask for the destination IP address is 0.0.0.0, the address for Dest IP Addr could have been anything. The mask for Source IP Addr must be 255.255.255.255 since an exact match is desired.

■Source IP Addr = 199.211.211.17

■Source IP address mask = 255.255.255.255

■Dest IP Addr = 0.0.0.0

■Destination IP address mask = 0.0.0.0

Note: To learn about IP addresses and masks, see Appendix C, “Understanding IP Addressing.”

3.Using the tables on page 13-7, find the destination port and protocol numbers (the local Telnet port):

■Proto = TCP (or 6)

■D. Port = 23

4.The filter should be enabled and instructed to block the Telnet packets containing the source address shown in step 2:

■On? = Yes

■Fwd = No

This four-step process is how we produced the following filter from the original rule:

+-#---

Source IP Addr---

Dest IP Addr-----

Proto-Src.Port-D.Port--

On?-Fwd-+

+----------------------------------------------------------------------

 

 

 

+

1

192.211.211.17

0.0.0.0

TCP 0

23

Yes No

 

 

 

 

+----------------------------------------------------------------------

 

 

 

+

 

 

 

 

 

 

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Netopia 4752 manual Filtering example #1
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4752 specifications

The Netopia 4752 is a versatile networking device that serves as a digital subscriber line (DSL) modem and router, designed to provide high-speed internet connectivity and advanced networking capabilities for home and small office environments. This device is notable for its reliability and ease of use, making it a popular choice among users looking for seamless internet access.

One of the main features of the Netopia 4752 is its support for various DSL technologies, including ADSL and ADSL2+. This compatibility ensures that users can achieve optimal bandwidth and speed, even on legacy DSL lines. The modem’s capability to handle downstream speeds of up to 24 Mbps allows for smooth streaming, gaming, and browsing experiences.

Equipped with a robust built-in router, the Netopia 4752 offers multiple Ethernet ports for direct wired connections, accommodating multiple devices simultaneously. This feature is especially beneficial in environments where multiple users need to access the internet without latency. Additionally, the device supports wireless connectivity, enabling users to connect their laptops, smartphones, and other Wi-Fi-enabled devices effortlessly.

Security is a crucial aspect of the Netopia 4752’s functionality. The device incorporates a built-in firewall and supports various security protocols, including WPA and WPA2, ensuring that users’ data remains protected from unauthorized access. The user-friendly web-based interface facilitates easy configuration of security settings, making it accessible even for those with limited technical knowledge.

The Netopia 4752 also features advanced Quality of Service (QoS) settings that allow users to prioritize bandwidth for specific applications or devices. This capability is crucial for households or offices that demand high performance for video conferencing, streaming services, or online gaming.

In terms of characteristics, the Netopia 4752 boasts a compact form factor, making it easy to integrate into any workspace without occupying much space. Its durable design ensures longevity, providing reliable service over time.

Overall, the Netopia 4752 stands out as a dependable DSL modem and router solution, with its high-speed internet capabilities, security features, and flexible connectivity options suitable for both home and small office users who require efficient and effective internet access.
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