Verify VLANs and trunking.

Use the show ip interface trunk command on S1 and the show vlan command on S2 to determine that the switches are trunking correctly and the proper VLANs exist. 

S1#show interface trunk

Port        Mode         Encapsulation  Status    Native vlan

Fa0/1       on           802.1q         trunking      1

Fa0/2       on           802.1q         trunking      1

Fa0/3       on           802.1q         trunking      1

Fa0/4       on           802.1q         trunking      1

Fa0/5       on           802.1q         trunking      1

Port      Vlans allowed on trunk

Fa0/1       1-4094

Fa0/2       1-4094

Fa0/3       1-4094

Fa0/4       1-4094

Fa0/5       1-4094

Port        Vlans allowed and active in management domain

Fa0/1       1,10,20,88

Fa0/2       1,10,20,88

Fa0/3       1,10,20,88

Fa0/4       1,10,20,88

Fa0/5       1,10,20,88   

Port        Vlans in spanning tree forwarding state and not pruned

Port        Vlans in spanning tree forwarding state and not pruned

Fa0/1       1,10,20,88

Fa0/2       none         A ← blocked due to spanning tree

Fa0/3       1,10,20,88

Fa0/4       1,10,20,88

Fa0/5       1,10,20,88>