Ran into an issue after updating a site to MS 12.27.    After the update, clients at the site reported poor connectivity to internal systems as well as internet.      Site consists of 2 x MX100 (HA Pair), 2 x MS425  as distribution stack, and 8 x MS350 access stacks.   MXs connected to MS425 stack.   MS350 stacks connected to MS425 stack with dual fiber in aggregated pair.    MS425 stack running L3 and is the STP root.   After 12.27 upgrade, clients complaining of slow connection speeds.   Clients getting decent download speeds, but upload speeds almost zero.    Running dual ISPs to MXs.   Issue existed with both ISP links.   Finally went onsite and tested the following: Tested directly from ISP handoff - no issue Tested directly from MX port - no issue Tested directly from MS425 port - no issue Testing from MS350 access switch port - ISSUE   Once the issue came up at the access switch, I removed the aggregation on the uplink fibers and the problem goes away.   That was a bit of a head scratcher as nothing changed in our configuration other than the firmware from 11.30 to 12.27.   Those aggregated links have been on that network since it was created almost 2 years ago with no issues.   I also have another location that is similarly configured and it is not exhibiting the same behavior.    What could have caused or could be causing this?   ... View more