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..
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..
The Distributed Update Algorithm
Distributed Update Algorithm (DUAL) is used by Enhanced IGRP to achieve fast, loop-free convergence with little impact on CPU cost and overhead. DUAL involves only the nodes affected by topology change and takes corrective action, such as sending queries about the lost route across only the affected nodes. Nodes that are unaffected simply reply that they have an alternate path. DUAL works well when more than one change occurs simultaneously because only the affe..
Enabling Syslog on a Unix Server
For most flavors of Unix and Linux, you simply need to modify the /etc/syslog.conf file on your Unix server to include the following entry (basic configuration): local7.info /var/log/rtrlog This example stores all router messages using the default logging f..
Because most enterprise networks have moved toward the 20/80 rule (where server and intranet/ Internet resources are centralized), end-to-end VLANs have become cumbersome and difficult to maintain. The 20/80 rule reverses the traffic pattern of the end-to-end VLAN: Only 20 percent of traffic is local, whereas 80 percent is destined to a remote resource across the core layer. End users usually require access to central resources outside their VLAN. Users must cross into ..
