you may remember me from the weird cogent route retention / loop
problem i brought up last week. it remains unsolved by cogent to date.
also remembering i'm a relatively new cogent customer, i recently
noticed some packets floating into my network that had cos and ipp
markings on them. i figured i'd try to find where they were coming
from, so i crafted up something like this and placed it inbound on my
two transits (cogent and xo), excluding network control markings.
from {
dscp [ af11 af12 af13 af21 af22 af23 af31 af32 af33 af41 af42
af43 cs1 cs2 cs3 cs4 cs5 ef ];
precedence [ 1 2 3 4 5 ];
}
all of it is coming in from cogent:
COGENT-NOT-BE -> 4217788987
XO-NOT-BE -> 0
i shifted all traffic to XO just to make sure. the XO counter doesn't budge.
seems like one transit is remarking everything to best effort before
sending to me (which is preferred), and the other is not.
am i odd to think that this is... odd?
i also get a remarkable amount of hits against these destinations
coming in on the cogent side, whereas i get none on the XO side.
show policy-options prefix-list PUBLIC-BAD-NETS
10.0.0.0/8;
169.254.0.0/16;
172.16.0.0/12;
192.168.0.0/16;
224.0.0.0/4;
ryan
cogent is well known not to filter in any useful way... in terms of sources that should not be there, we see the same thing (or did the last time I looked).
John van Oppen
Spectrum Networks
Direct: 206-973-8302
Main: 206-973-8300
you may remember me from the weird cogent route retention / loop
problem i brought up last week. it remains unsolved by cogent to date.
also remembering i'm a relatively new cogent customer, i recently
noticed some packets floating into my network that had cos and ipp
markings on them. i figured i'd try to find where they were coming
from, so i crafted up something like this and placed it inbound on my
two transits (cogent and xo), excluding network control markings.
from {
dscp [ af11 af12 af13 af21 af22 af23 af31 af32 af33 af41 af42
af43 cs1 cs2 cs3 cs4 cs5 ef ];
precedence [ 1 2 3 4 5 ];
}
all of it is coming in from cogent:
COGENT-NOT-BE -> 4217788987
XO-NOT-BE -> 0
i shifted all traffic to XO just to make sure. the XO counter doesn't budge.
seems like one transit is remarking everything to best effort before
sending to me (which is preferred), and the other is not.
am i odd to think that this is... odd?
It's not that uncommon, but it's one of the reasons to sanitize on
ingress if you don't want to see that (and absolutely if you're reusing
them).
i also get a remarkable amount of hits against these destinations
coming in on the cogent side, whereas i get none on the XO side.
show policy-options prefix-list PUBLIC-BAD-NETS
10.0.0.0/8;
169.254.0.0/16;
172.16.0.0/12;
192.168.0.0/16;
224.0.0.0/4;
you can add
100.64.0.0/10 to that list. 
i retract the blurb about the bad destinations coming in from cogent, as
that obviously doesn't make a lot of sense. the spoofed traffic is actually
arriving on my connection into an ix fabric. thx to john frazier for
tickling my brain on that one.
the upped markings, however, are definitely coming in from cogent.