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Issue with some unnamed ISP's in northern north america, RFC 1918 Violation


From: wolf1098--- via NANOG <nanog () lists nanog org>
Date: Tue, 10 Mar 2026 21:13:23 -0000

One of the fibre providers, they are issuing static ips, which is good, but the way the statics are handled. The 
modem/router, if you want static ips, requires it to be in router mode, you can't bridge. it seems the router's static 
ip gateway does some bgp towards the isp to route the static ip's block assigned to the customer to it, via its dhcp 
established route??? idk. ------ THE big issue, which is, since it has to be in router mode. they end up with a dynamic 
ip, that is the gateway for dhcp RFC1918 addresses, that are on its lan, sounds reasonable, but as a tertiary use, the 
static ip WAN gw stack, LOADS IN ON the same L2 lan bridge, side by side with the RFC 1918 space, without even 
attempting to put it in a tagged vlan. don't do this.... without using a custom linux router, good luck using both the 
static ips block, and the double 'natted' dynamic ip.
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