Using Regular Expressions to Match AS_PATH

A Cisco IOS AS_PATH filter has one or more configured lines, with each line requiring a regex. The logic is then applied as follows: 1. The regex of the first line in the list is applied to the AS_PATH of each route. 2. For matched NLRI, the NLRI is passed or filtered based on that AS_PATH filter’s configured permit or deny action. 3. For unmatched NLRI, Steps 1 and 2 are repeated, using the next line in the AS_PATH filter, analyzing all NLRI yet to be matched by this ..

Pure Multipoint NBMA Networks

Pure multipoint Enhanced IGRP divides the configured bandwidth evenly across each virtual circuit. However, you must ensure that this does not overload each virtual circuit. The formula for multipoint is as follows:   Bandwidth × number of VC (virtual circuits)   For example, if you have an access line speed of T1 and there are four virtual circuits, each with 56 Kbps CIR, the bandwidth should be set to 4 × 56 Kbps = 224 Kbps. This will ensure that p..

Network Security Policies

IP networks are susceptible to unsecured intruders using a variety of different methods to gain entry. Through the campus, by dialup, and through the Internet, an intruder can view IP data and attack vulnerable network devices. IP networks must provide network security for the following reasons: •    Inherent technology weaknesses All network devices and operating systems have inherent vulnerabilities. •    Configuration weaknesses Common c..

Using SNMP to Copy a New IOS Image

Before you can upload or download the router's IOS image to a TFTP server, you have to set up a valid read-write SNMP community string: Router#configure terminal Enter configuration commands, one per line.  End with CNTL/Z. Router(config)#snmp-server community ORARW rw Router(config)#end Then you can download a copy of your router's current IOS file to your TFTP server with the following Unix commands: Freebsd% touch /tftpboot/c2600-jk9o3s-mz.122-7a.bin Freebsd% chmod ..

Virtual Links

 OSPF area design requires the use of a backbone area, area 0, with each area connecting to area 0 through an ABR. However, in some cases two backbone areas exist; in other cases, a nonbackbone area may not have a convenient point of connection to the backbone area, for example: Case 1. An existing internetwork needs to add a new area, with a convenient, low-cost connection point with another nonbackbone area. However, that connection does not give the new area any conn..