Help with broken routing in MTL (AS577 174 11647) Bell, Cogent, Me

Fri Jun 24 17:49:51 UTC 2022

We noticed random traffic originating from AS577 stopped getting to our 
ASN via Cogent in Montreal at around 00:24 this morning. Based on the 
pattern I am guessing a broken next hop on one leg of a larger link ?  
e.g. IP traffic leaving AS577 towards IP addresses in one of my /19s 
will 100% work for certain IPs and 100% fail for others all within that 
same /19.

e.g. from 142.112.93.72 (an IP originating in AS577) to one of the IPs 
below in my 64.7.128.0/19

64.7.134.1 100% fail
64.7.134.2 100% pass
64.7.134.3 fail
64.7.134.4 fail
64.7.134.5 fail
64.7.134.6 fail
64.7.134.7 100% pass
64.7.134.8 100% fail
64.7.134.9 fail
64.7.134.10 pass

Its just packets towards my ASN that are failing. Packets TO  577 via 
174 all work fine.

Traceroutes good and bad all look like this

% traceroute -s 142.112.93.72 -q1 -I 64.7.134.2
traceroute to 64.7.134.2 (64.7.134.2) from 142.112.93.72, 64 hops max, 
48 byte packets
  1  lns5-ottawa23_lo0.net.bell.ca (64.230.11.188)  10.507 ms
  2  64.230.98.68 (64.230.98.68)  17.539 ms
  3  tcore4-montreal02_1-9-0-0.net.bell.ca (64.230.79.127) 18.150 ms
  4  cr02-mtrlpq02ho6_bundle-ether1.net.bell.ca (142.124.127.251)  13.787 ms
  5  bx1-montrealgz_et-0-0-5.net.bell.ca (64.230.26.135)  12.237 ms
* 6  **
  7  be2089.ccr21.ymq01.atlas.cogentco.com (154.54.45.113) 13.337 ms
  8  be3259.ccr31.yyz02.atlas.cogentco.com (154.54.41.205) 17.969 ms
  9  sentex.demarc.cogentco.com (38.104.158.78)  17.126 ms
10  agas-core1-em0.sentex.ca (67.43.129.251)  39.960 ms
11  agas-lns1c-c.sentex.ca (64.7.129.19)  32.171 ms
12  orbiting.anysphere.com (64.7.134.2)  49.336 ms

% traceroute -s 142.112.93.72 -q1 -I 64.7.134.1
traceroute to 64.7.134.1 (64.7.134.1) from 142.112.93.72, 64 hops max, 
48 byte packets
  1  lns5-ottawa23_lo0.net.bell.ca (64.230.11.188)  10.229 ms
  2  64.230.98.66 (64.230.98.66)  13.346 ms
  3  tcore3-montreal02_hu2-4-0-2.net.bell.ca (64.230.78.252)  12.660 ms
  4  cr01-mtrlpq02ho5_bundle-ether1.net.bell.ca (142.124.127.233) 12.423 ms
  5  bx1-montrealgz_et-0-0-1.net.bell.ca (64.230.26.133)  12.225 ms
*6  **
  7  *
  8  *
  9  *
10  *
11  *

Not sure if hop 6 is a Bell device or Cogent device. I have a ticket 
open with Cogent, but they dont see any issues in their network. I am 
not a direct customer of Bell, so I cant open a ticket with them. Was 
hoping someone from AS577 would see this and take a look.

     ---Mike