Clarification needed on how to trunk two Dell S4048T-ON switches

Switch 1 (ethernet 1/1/48)

vlan 20

ip address 10.20.30.1/23

no shutdown

ethernet 1/1/48

mtu 9198

switchport mode trunk

switchport trunk allowed vlan 20

Switch 2 (ethernet 1/1/48)

vlan 20

ip address 10.20.30.2/23

no shutdown

ethernet 1/1/48

mtu 9198

switchport mode trunk

switchport trunk allowed vlan 20

*My question: my expectation is I should be able to ping 10.20.30.2 from switch 1.  

From switch 2, I should be able to ping 10.20.30.1.

This does not work and states destination unreachable.

This continues to fail unless I remove with switchport trunk allowed vlan 20 from both interfaces on both switches and replace it with switchport access vlan 20.  Then I can ping as much as I want.

Both interfaces and vlans are up and line protocol up.

My thought is that setting switchport access vlan 20 locks the port to only vlan 20.  It shouldn't work as a trunk allowing all specified vlans.  Can someone please clarify if I understand this right?

But my main question, is why do the pings not work with the config I outlined above?

Thanks!