Traffic destined for 100.114.128.0/24

Wed Apr 8 18:54:46 UTC 2020

On 4/8/20 2:42 PM, Drew Weaver wrote:
> Hello,
> 
> I’ve noticed over the past couple of weeks that some hosts on a network 
> I manage appear to be trying to reach hosts in this network 100.114.128.0/24
> 
> It’s an IANA reserved block but I’m really not sure what it’s used for. 
> I just notice it keeps coming up but it doesn’t have a route.
> 
> Has anyone else been seeing this?

This is part of the RFC6598 space for carrier-NAT deployments.  If 
you're seeing traffic inbound to your network to those addresses, 
someone's presumably got a default toward you and a hole in their 
internal routing table.  If you're seeing traffic outbound toward those 
addresses, some of your customers have somehow picked up a configuration 
expecting some sort of service there.

Inbound traffic toward your network from or to those addresses is 
effectively a bogon.  Outbound traffic from/to those addresses means you 
have a misconfiguration somewhere (presumably unintentional and perhaps 
some poorly behaved automatic config on a CPE).
-- 
Brandon Martin