Route Filtering and Route Summarization

This section focuses on four popular tools used to filter BGP routes: ■ Distribution lists ■ Prefix lists ■ AS_PATH filter lists ■ Route maps Additionally, the aggregate-address command can be used to filter component subnets of a summary route. This section covers these five options. (Filtering using special BGP COMMUNITY values will be covered at the end of the chapter in the section titled “BGP Communities.”) The four main tools have the following features in..

Redistribution Using Default Settings

The first example configuration meets the following design goals: ■ R1 redistributes between each pair of IGPs—RIP, EIGRP, and OSPF. ■ Default metrics are used whenever possible; when required, the metrics are configured on the redistribute command. ■ Redistribution into OSPF uses the non-default subnets parameter, which causes subnets to be advertised into OSPF. ■ All other settings use default values. Example 11-1 shows R1’s configuration for each routing..

Required Commands for Configuring EIGRP

Like other interior routing protocols, the template for an EIGRP configuration involves turning on the protocol and identifying participating interfaces. EIGRP also uses an autonomous system (AS) to group routers. To run EIGRP, you must enable the following three items:  • The EIGRP process— The routing protocol needs to be started on the router.  • The EIGRP autonomous system number— Routers in the same administrative domain should be identified and group..

Asynchronous Communications and Access Devices

An asynchronous (async) communication is a digital signal that is transmitted without precise clocking. The RS-232 session between a router and PC through the console connection is an example of async communications. Such signals generally have different frequencies and phase relationships. Asynchronous transmissions usually encapsulate individual characters in control bits (called start and stop bits) that designate the beginning and the end of each character. For example, t..

Filtering Based on Noncontiguous Ports

To filter noncontiguous ports, use the following commands: Router2#configure terminal Enter configuration commands, one per line.  End with CNTL/Z.Router2(config)#ip access-list extended OREILLYRouter2(config-ext-nacl)#permit tcp any host 172.25.100.100 eq 80 23 25 110 514 21Router2(config-ext-nacl)#endRouter2#   Cisco introduced the ability to filter noncontiguous ports in IOS Version 12.3(7)T.   Historically, Ci..