Traffic destined for 100.114.128.0/24

[lists.nanog at monmotha.net (Brandon Martin)]

On 4/8/20 2:42 PM, Drew Weaver wrote:
> Hello,
> 
> Iâ??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
> 
> Itâ??s an IANA reserved block but Iâ??m really not sure what itâ??s used for. 
> I just notice it keeps coming up but it doesnâ??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