[c-nsp] something a little different rfc1918 from transit networks?

[David Freedman]

Drew Weaver wrote:
> SLOT 6:Nov 12 17:10:36.121 EST: %SEC-6-IPACCESSLOGP: list 175 denied tcp 192.168
> .1.2(0) (GigabitEthernet2 ) -> ip.add.re.ss(0), 1 packet
> SLOT 10:Nov 12 17:10:39.841 EST: %SEC-6-IPACCESSLOGP: list 175 denied tcp 192.16
> 8.1.2(0) (GigabitEthernet0 ) -> ip.add.re.ss(0), 1 packet
> 
> This is the first time I can say I've ever seen this, I'm assuming its spoofed but I'm not going to rule anything out here.
> 
> Lets say that slot 6/2 is connected to one transit carrier and slot 10/0 is connected to another transit carrier (which is the case)

This is normal, somebody reachable via your upstream (posibly a 
downstream or peer without uRPF configured) has been sending packets 
sourced from these addresses.


> 
> I'm trying to figure out if those 192.168.1.2 packets that my ACL 175 are denying are actually SRC'd from 192.168.1.2 or they're spoofed, 
> is there anyway to know that for sure?

Of course they are sourced from 192.168.1.2, in so much as somebody has 
created packets with this as the source address and their network 
provider has not filtered them.

> 
> Any thoughts or advice?

Its normal, providing you filter RFC1918 as part of your standard bogon 
filtering you shouldn't need to lose any sleep over it.

Dave.


> 
> Thanks,
> -Drew
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