iSCSI storage 3800 can`t see initiator ESXi after adding a switch Cisco SX350X

Hi.

We have Dell MD3800 storage directly attached to 2 ESXi hosts (Dell R630), iSCSI, 1Gb T-base.

We bought additional Dell 4240 storage and two Cisco SX350X 10G switches to deploy SAN.

We have mandatory settings on Cisco switches for iSCSI (jumbo frame, flow control, iSCSI enabled, flow to TCP 3260 allowed).

When we connect ESXi host to a storage (for example an old 3800) through the Cisco switch, rescan switches in vsphere - we can`t see data storage and storage can`t see initiator (no additional settings on the storage or the host made).

So the question is - what is a procedure for changing topology from direct attached iSCSI to network connected iSCSI? Should we change initiator/LUN/whatever... We just add a switch between iSCSI partners.

And we also can`t see iSCSI initiator from newly attached to the same switch Dell 4240 storage.

It seems that Cisco SX350X blocks iSCSI traffic somehow... but:

1. We have all the settings needed on the switch.

2. If I plug a notebook into the same switch and make powershell 'test network connection' to ip_storage:3260 I get positive result.

Thanks in advance for any help!