North American Network Operators Group|
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Re: ISPs Blocking Private Addresses?
Peter, > Do most ISPs explicitly block private IP addresses (e.g. 10.X.X.X) at their > borders? > > Do the "default-less" ISPs filter private addresses or do they let > routing/forwarding do the work? More clueful ISPs do in fact block private address space exchange via BGP. Many also filter. Smaller ISPs tend to miss these steps, and there is frequently someone advertising private space at the NAPs from time to time. And some believe it, surprisingly. Many cable networks, like Rogers and @Home use net 10 for numbering internal devices for SNMP survellience, like modems and switches. While INTERNIC may not mandate it, they are sensitive to 2 IP addresses per household drawn from the public space. As such, when @Home and Rogers merged networks, there was some private address space reconcilication required. Thus, you cannot assume that private address space is not routed "privately" within a given ISP's backbone. Needless to say, they are usually very vigilant about route and packet filtering. Regards, Eric Carroll [email protected] Tekton Internet Associates