Can an LTM be connected to a Cisco FEX (fabric extender)?

No, single arm implies a SINGLE VLAN. i.e. No Routing. This is the traditional description of single arm. Number of switch environments is immaterial when describing single versus non-single arm (Unless you're making up your own terminology instead, in which case you can call it what you like). And what you'd call a VE I have no idea.. 0 arms because it has no physical interfaces?

Anyway. We can argue semantics later. Preferably over a Pint of Rebellions finest.

So you have only single LACP trunk connected to both 7010, correct?

Yes. Correct. However, the Viprion DOES have a redundant link to the Nexus... There are at least TWO interfaces in the BigIP trunk. To a single vPC... Which is across TWO Nexus switches. In fact some of mine have 4 interfaces spread across 2 blades. Still a single vPC though. Because with vPC's you don't have to worry about spanning tree.

What happens if F5 failed over to standby or primary vPC failed?

Well, if the vPC failed, your nexus is probably not working anyway. (Unless it's a config problem. And they're always difficult to plan against). In fact I have yet to lose a vPC because of anything other than a complete switch failure (They're even reasonably robust against vPC peer keepalive failures so far)

H