We are observing an issue with the core network in Fremont.
Update: 8:35:
The network got a lot more stable, the issue seems to be a memory leak on a core router.
We are now planning to reboot the affected router.
Update: 11:30:
We are once again seeing this issue, we are working on a fix.
Update: 13:30:
After a reboot of the router in question, the network is stable again - we are observing the router closely and publish a post mortem in due course.