Using AS path lists as path filters

BGP: Configuring AS Path Filters

Implicitly exclude a neighbor

Using AS path lists as path filters

When an AS path list has been created, it can be applied to filter incoming or outgoing update messages for a particular BGP peer, by using the following commands in BGP router mode for the AS.

Filter incoming updates (received from a particular neighbor):

awplus(config-router)#neighbor <neighbor> filter-list <list-name> in

Filter outgoing updates (destined for a particular neighbor):

awplus(config-router)# neighbor <neighbor> filter-list<list-name> out

The router will then compare the AS path attribute in BGP update packets with each entry in the AS path list until a match is found. If the AS path list entry that matches has the parameter permit, then the update packet will be allowed through by the filter. If the matching entry has the parameter deny, then the update packet will be blocked by the filter.

Note: All update packets whose AS paths do not explicitly match an entry in the AS path list will be dropped, because the list ends in an implicit deny all entry.

Example: AS path filters

Discard or allow routes from a neighbor

This example expands on the basic configuration in "BGP: Example" on page 8.

First, it creates an AS path filter on the AlliedWare Plus switch that explicitly includes only AS 23456. AS path filters end in an implicit deny clause, so this filter implicitly excludes

AS 34568. After demonstrating that AS 34568 is excluded, the example then adds an entry to the filter to explicitly allow AS 34568.

1.If you previously configured a distribute filter, as shown in "Example: Distribute filters" on page 12, remove it from the neighbor definition.

awplus(config)# router bgp 34567

awplus(configrouter)# no neighbor 45.45.45.46 distribute-list1301 in

2.Create an AS path access list that includes AS 23456. awplus(config)# ip as-path access-list list1 permit 23456

3.Set that access list as the in-filter for the BGP neighbor 45.45.45.46.

awplus(config)# router bgp 34567

awplus(config-router)#neighbor 45.45.45.46 filter-list list1 in

Page 18 Use Route Maps and Other Filters to Filter and Alter BGP and OSPF Routes

Page 17 Page 19
Page 18
Image 18
Allied Telesis x908 Using AS path lists as path filters, Example AS path filters, Discard or allow routes from a neighbor
Page 17 Page 19

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