(From DMIT NOC)
Los Angeles Major issue:

Widespread underlying fiber-optic cable failures affecting Cogent and Zayo have led to reduced network stability in the Los Angeles area.
Due to nested leasing arrangements within US Tier-1 backbones, the impact has extended to GTT and Arelion.
Packet loss has been observed on routes from Los Angeles toward the East (including Europe); the DMIT NOC has temporarily removed some of the most severely affected routes.

Some AS174 and AS3257 single home networks are not able to be migrated for network reachablity reason.

https://tranzact.zayo.com/#!/networkStatus

https://ecogent.cogentco.com/network-status

image.webp

DMIT has isolated the issue, except AS174 and AS3257 single home network.

Nevertheless, Cogent's Los Angeles metropolitan area network is experiencing a severe outage, with some parts of the network unable to access the Internet at all.

Screenshot shows the reachability of DMIT's Cogent interface and the location of failure.

Since this issue has been isolated, traffic was divert to NTT, GSL, Arelion and GTT. DMIT will stop update the network status of Cogent.
Both inbount and outbount routes are removed from Cogent 8hrs ago, since it's unusable.