BGP: Configuring Prefix Filters

BGP: Configuring Prefix Filters

Prefix filters use prefix lists to filter particular routes on the basis of their prefixes. Prefix filters and distribute filters both filter individual routes out of BGP update packets. They are mutually exclusive.

About prefix lists

A prefix list is a list of prefix entries. Each entry specifies a particular prefix, a mask length or range of mask lengths, and whether or not those prefixes are deemed to explicitly match or explicitly not match the prefix list.

A prefix list entry is created with the command:

awplus(config)# ip prefix-list <list-name> [seq <number>] {denypermit} {any<ipadd>/<prefix-length>} [ge <minimum-length>] [le <maximum-length>]

You can choose to give an entry a sequence number by using the optional seq parameter. If you do not, the switch assigns sequence numbers in steps of 5 (number 5, 10, 15 etc.) and puts the new entry at the end of the list of entries.

To see entries and their numbers, use the command:

awplus# show ip prefix-list

Mask length

You can specify a single prefix mask length, or you can use the ge and le parameters to specify a range of mask lengths for the entry to match.

If you set the mask length to:

a single mask length (by specifying neither the ge nor the le parameter), then a route matches against this entry if its prefix mask length is exactly that length.

a range of mask lengths, then a route matches against this entry if its prefix mask length is greater than or equal to ge and less than or equal to le.

For example, to deny the IP addresses between 10.0.0.0/14 (mask of 255.252.0.0) and 10.0.0.0/22 (mask of 255.255.252.0) within the 10.0.0.0/8 (mask of 255.0.0.0) addressing range, use the command:

awplus(config)# ip prefix-list mylist deny 10.0.0.0/8 le 22 ge 14

The mask length (8 in this example) must be less than the value specified for the ge parameter. This mask defines the range of subnets that the matching subnets must fall within.

Page 22 Use Route Maps and Other Filters to Filter and Alter BGP and OSPF Routes

Page 21 Page 23
Page 22
Image 22
Allied Telesis x908, X8100 manual BGP Configuring Prefix Filters, About prefix lists, Mask length
Page 21 Page 23

X8100, x908 specifications

The Allied Telesis x908 and the SwitchBlade x900 series of network switches are cutting-edge solutions designed to address the demands of modern networking environments. These switches are known for their high performance, reliability, and robust feature sets, making them ideal for enterprise and service provider networks.

The Allied Telesis x908 series consists of modular and chassis-based systems that can accommodate a variety of network configurations. One of the main features of the x908 series is its ability to offer high scalability with support for a large number of ports. This makes it suitable for data centers and large enterprise networks where space and bandwidth optimization are critical.

In addition to scalability, the x908 series supports advanced Layer 2 and Layer 3 switching capabilities. This allows for efficient traffic management and routing, ensuring that data is delivered swiftly and reliably. The x908 also incorporates intelligent features such as Quality of Service (QoS), which prioritizes critical network traffic, ensuring that time-sensitive data—like voice and video—maintains its quality during transmission.

The SwitchBlade x900 series takes this functionality further with its innovative modular architecture. This allows organizations to configure their networks to meet specific needs by choosing from a variety of interface cards and service modules. The SwitchBlade x900 also supports advanced security features such as Access Control Lists (ACLs) and VLAN segmentation, which provide enhanced protection against unauthorized access and network threats.

Another hallmark of the x908 and SwitchBlade series is their support for high-speed Ethernet technologies, including 10G and 40G Ethernet. This enables organizations to keep pace with the increasing bandwidth demands of applications and services, particularly in cloud computing and data-intensive workloads.

Both the x908 and the SwitchBlade x900 series are designed with energy efficiency in mind, featuring power-saving technologies that reduce overall operational costs. Coupled with Allied Telesis' management tools, which provide detailed analytics and monitoring, network administrators can optimize performance and energy consumption simultaneously.

In summary, the Allied Telesis x908 and SwitchBlade x900 series offer a comprehensive suite of features, high performance, scalability, and advanced networking technologies. They represent a strategic investment for organizations looking to build resilient, efficient, and future-proof network infrastructures.
Top Page Image Contents