I have done demonstrations in the past on Vlan Hopping and this usually comes down to configuration of the devices and the series of switches.
For example, in Cisco's Catalyst family of switches, DTP is set to 'desirable' by default, meaning that it is willing to trunk and all you have to do is tell that port that you want to trunk and it will create that trunk link and negotiate the encapsulation protocol (Usually 802.1Q). I demonstrated this using a tool called Yersinia.
Some families of Cisco devices don't even use DTP at all and use a different process and/or protocol for negotiation of a trunk link.
Another variable that has to come together for this attack to happen is the use of the Native VLAN.
An easy way to prevent such attack is to not place any hosts in the Native VLAN and/or set DTP mode to nonegotiate.
Overall, you'll have to see if the IE series uses DTP. If it doesn't but uses something similar then make sure your ports will not auto trunk with any device that asks for it. This would essentially prevent a rogue device from trunking and sending double encapsulated packets which also needs to make use of the Native VLAN.
To say your devices are vulnerable or not is hard without seeing the configuration but the above methods with help prevent the attack from succeeding.