ArubaOS-CX Access vs Trunk Ports: VLAN Configuration Scenarios

ArubaOS-CX switches use a simple but easy-to-misread model: an interface is an access port when it carries a single untagged VLAN, and a trunk port when it carries multiple VLANs with a native VLAN plus an allowed list. This article reproduces the official ArubaOS-CX Layer-2 Bridging Guide scenario in which three switches isolate traffic for computers, servers and DHCP clients, with every command and the expected show output.

Access vs Trunk: The ArubaOS-CX Model

• Access interface - carries traffic for one VLAN only; untagged frames belong to the configured access VLAN (vlan access <ID>).
• Trunk interface - carries one or more VLANs; vlan trunk native <ID> sets the untagged VLAN and vlan trunk allowed <list> defines which VLANs may cross the trunk.
• Native VLAN tagging - add the tag keyword (vlan trunk native 6 tag) when the native VLAN must be sent tagged; untagged traffic is then dropped except BPDUs.

Scenario Configuration, Switch by Switch

Create the VLANs and a trunk LAG on switch A and B so VLANs 4 and 25 (tagged and untagged) reach switch B:

switch# config
switch(config)# vlan 4,25
switch(config)# interface lag 1
switch(config-lag-if)# no shutdown
switch(config-lag-if)# vlan trunk native 25
switch(config-lag-if)# vlan trunk allowed 4,25
switch(config-lag-if)# interface 1/1/1
switch(config-if)# no shutdown
switch(config-if)# lag 1

For switch C, VLANs 6 and 17 travel over LAG 3 with the native VLAN tagged:

switch(config)# vlan 6,17
switch(config)# interface lag 3
switch(config-lag-if)# vlan trunk native 6 tag
switch(config-lag-if)# vlan trunk allowed 6,17

Finally connect the server as a plain access port on switch A:

switch(config)# vlan 100
switch(config-vlan-100)# interface 1/2/32
switch(config-if)# no shutdown
switch(config-if)# vlan access 100

Verification Commands

switch# show vlan
switch# show interface lag1
switch# show interface 1/2/32

On the LAG output check the VLAN Mode (native-untagged vs native-tagged), Native VLAN and Allowed VLAN List fields. On the access port check VLAN Mode: access and Access VLAN: 100, then confirm the Rx/Tx counters are incrementing so you know traffic is really flowing.

Related Reading on This Site

Brush up on ArubaOS-CX native VLAN tagging and the Aruba 8325 AOS-CX VLAN access/trunk CLI examples.

原文链接：https://arubanetworking.hpe.com/techdocs/AOS-CX/10.15/HTML/l2_bridging_4100i-6000-6100-5420-6200/Content/Chp_vlans/vla-sce.htm