Bright House ISP routing private IPs on the Internet

iVenture_Solutions
iVenture_Solutions used Ask the Experts™
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Recently I found our ISP (Bright House) is routing private IP addresses publicly. Has anyone else run into this?

We have a network ID of 10.10.12.0/24 internally. For some reason when I do a tracert to other 10.10.x.0 networks and some 192.168.x.0 networks I can see the packets are being routed through our firewall, through our ISP's network and into someone else's private network. I can even connect to devices on these remote network by private IP using HTTP.

Bright House has explained that they use 10.x.x.x addresses publicly and don't support clients of theirs using 10.x.x.x network IDs in their private LANs. Has anyone else run into this?
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Top Expert 2010
Commented:
Yes, I see this all the time; an ISP can route RFC1918 space (Private space) in their network all they want. They (Bright House) can also try and advertise rfc1918 space to their upstream providers (Transit peers) via BGP but will get filtered and stop there. As long as you have a firewall I would not worry about. What you are seeing is perfectly normal and basic routing principles.

Billy

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Commented:
Thx for the response. The strange this we have a firewall.. errr a router. Our little metal box LINKSYS apparently isn't doing it's job it seems.
Top Expert 2010

Commented:
well, it is doing exactly what it is designed to do; your router.... is routing, nothing more, nothing less. Your hosts have a default gateway (Linksys router), your router has a default gateway (ISP) and all other more specific routes are on the the routers that your default gateway terminates on. If it is anything, it is your ISP that is not going a good job filtering traffic from one subnet to another. The fact they allow ICMP echo and replies and who knows what other interesting IP traffic from your network (And/or other customers) to reach their rfc1918 space is not too bright in my opinion; just my 2 cents.

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