[f-nsp] SI & FGS not forwarding

[Rob Heilman]

I have an issue that seems so basic yet I can not make headway against it.  I have had the following layout running for years:

[FGS648-01]=[SI-GTE-01]=[SI-GTE-02]=[FGS648-02]

Where the = symbols indicate a 4 port GE trunk carrying 2 VLANS via 802.1q.  Suddenly all devices hanging off of FGS648-02 can not communicate with any devices on the other switches in either VLAN.  The can however communicate with each other inside FGS648-02.  No config changes, no reboots, FW changes, etc. happened anywhere near the time of failure.  

I have tried reboots of the switches.  Changed the link to a single untagged vlan.  Even reduced the connection to a single GE link between SI-GTE-02 and FGS648-02.  Nothing seems to resolve the issue.  Has anyone else experienced this?  Any suggestions on how to better diagnose or resolve?

-Rob Heilman