Policy Routing Based on Traffic Source
Consider the example shown in Figure 8-6. Assume that AS1 was assigned network numbers from two different providers. The 10.10.10.0/24 range was taken from AS3, and the 11.11.11.0/24 range was taken from AS4. AS1 wants to have any traffic originated from its 10.10.10.0/24 networks to be directed toward AS3 and traffic from its 11.11.11.0/24 networks to be directed to AS4, irrespective of the traffic's final destination. AS1 could use policy routing to achieve this requirement..
Dissecting the Component Parts of an IP Address
First, deducing the size of the three parts (classful view) or two parts (classless view) of an IP address is important, because it allows you to analyze information about that subnet and other subnets. Every internetwork requires some number of subnets, and some number of hosts per subnet. Analyzing the format of an existing address, based on the mask or prefix length, allows you to determine whether enough hosts per subnet exist, or whether enough subnets exist to sup..
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 ..
Generating a Report of Interface Information
The netstat.pl script uses SNMP to gather IP subnet information from a list of routers. This ensures that the information is accurate and current. The script gathers all of the pertinent information about each router's IP interfaces and outputs this information as a CSV file. The netstat.pl script requires Perl and NET-SNMP and expects to find both in the /usr/local/bin directory. For more information on Perl or NET-SNMP, please see Appendix A. If you keep these programs in a..
The router will keep NAT entries in the translation table for a configurable length of time. For TCP connections, the default timeout period is 86,400 seconds, or 24 hours. Because UDP is not connection based, the default timeout period is much shorteronly 300 seconds, or 5 minutes. The router will remove translation table entries for DNS queries after only 60 seconds. You can adjust these parameters using the ip nat translation command, which accepts arguments in seconds: ..
