I have been reading Cisco's "Essential IOS Features Every ISP Should Consider" document and came across a section called Martian and RFC1918 networks. It is discussing different bogus or reserved networks that should be filtered by every ISP. In the list are some addresses I thought were legal and after checking the ARIN Whois database, some of them seem to be. Can anyone give me some additional information as to the need to filter the following networks: 1.0.0.0 reserved for IANA 19.255.0.0 this belongs to Ford 59.0.0.0 reserved for IANA 129.156.0.0 this belongs to SUN 169.254.0.0 IANA use for local link numbers??? 192.0.2.0 reserved for IANA 192.5.0.0 no ARIN match 192.9.200.0 no ARIN match 192.9.99.0 this belongs to SUN If you can elaborate on what they are used for and if any problems would arise from filtering these networks, it would be appreciated. If you could also please include where you found the information, I would appreciate it. Some of them belong to companies, so why would you filter them? Are they development networks for Ford and SUN? Are there any other martian networks that should be filtered? Here is the URL for the doc if anyone is interested: http://www.cisco.com/public/cons/isp/documents/IOSEssentialsPDF.zip Thanks in advance! Ron Fuller, CCDP, CCNP-ATM, MCNE, MCP 3X Corporaton rfuller@3x.com