Hi,
RSTP blocking the port probably suggests presence of a loop since RSTP has a single STP instance and would look at BPDUs from VLAN1 only and completely STP block the port [all VLANs inclusive] if a loop is detected.
With VSTP the mac-address table also indicates MAC addresses flapping with 38:20:56:11:24:01 probably being the facing 2960?
Is there any possibilities of having a loop in that topology?
Below commands could provide a picture of the STP topology:
show spanning-tree show spanning-tree bridge show spanning-tree interface
show spanning-tree interface detail
A useful resouce below for STP Interop b/w Juniper & Cisco:
http://www.juniper.net/us/en/local/pdf/implementation-guides/8010002-en.pdf
One of the catching points with VSTP is:
With Cisco switches, VLAN 1 complies with the IEEE spanning-tree specification. Currently the EX Series switches
cannot process BPDUs on VLAN 1 with Cisco switches. If there is a trunk port configured between Cisco switches and
Juniper EX Series switches, then the VLAN that is configured as the native-vlan than that VLAN (native-vlan) will treat
the BPDUs as a regular multicast and flood the BPDU.
"Note: When you configure VSTP with the set protocol vstp vlan all command, VLAN ID 1 is not set; it is excluded so that the configuration is compatible with Cisco PVST+. If you want VLAN ID 1 to be included in the VSTP configuration on your switch, you must set it separately with theset protocol vstp vlan 1 command."