Hello I have two switches connected together.
Switch#1 has it's interface as an ACCESS port (VLAN 31).
Switch#2 has it's interface configured as a TRUNK (allowing VLAN 31 and VLAN 41 with native VLAN 1) n.b. native VLAN 1 SVI is disabled so it cannot route.
They can both ping each other on the IP addresses of VLAN 31. How can this be ?
I understand that on this 2960 switch an Access port will accept a tagged frame if that tag is the same as it's VLAN ID.
BUT, I don't understand how the return traffic can succeed i.e. the return traffic will be going out untagged from Switch#1 Access port and entering the Switch#2 trunk, The trunk will then place it in to the native vlan which is VLAN 1. I have no VLAN 1 SVI configured how is this working i.e how does the traffic make it the SVI of VLAN 31 ?
I can only think that the traffic coming from Switch#1 access port is tagged somehow with VLAN 31 --OR-- because Switch#2 has an SVI for VLAN 31 it automatically works when receiving incoming untagged traffic in the subnet range of VLAN 31 ?
Cisco C2960S- SWITCH 1: configured and operating as a trunk
Name: Gi1/0/1
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: 31,41
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Cisco WSC3850 switch 2: Configured and operating as an ACCESS port.
Switchport: Enabled
Administrative Mode: static access
Operational Mode: static access
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: native
Negotiation of Trunking: Off
Access Mode VLAN: 31 (VLAN0031)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
