Joachim Wiberg
c3d17586fd
Fix #1506: restore the VLAN interface documentation that was lost when networking.md was split into per-topic pages. Content adapted from the v25.11.0 networking.md VLAN section, plus a new "Stacked (Q-in-Q)" section showing `eth0.10.20`-style nesting and the layered `show interface` rendering of the parent chain. Update the interface-type table in networking.md to point at the new vlan.md instead of the dangling ethernet.md#vlan-interfaces anchor. ChangeLog: document the user-facing changes on this branch (YANG model upgrade, layered show interface output, auto-negotation typo fix) and the new VLAN documentation. Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
3.3 KiB
VLAN Interfaces
A VLAN interface is an interface stacked on top of another Linux interface
that filters traffic for a single 802.1Q VID. tcpdump on a VLAN interface
shows only frames matching that VID, compared to all VIDs when listening
on the lower-layer interface.
This page covers VLAN interfaces stacked on Ethernet, on a VLAN-filtering bridge, and on other VLAN interfaces. For VLAN handling inside a bridge (port VIDs, tagged/untagged membership, pvid), see VLAN Filtering Bridge.
On Top of an Ethernet Interface
A VLAN interface for VID 20 on top of an Ethernet interface eth0 is by
convention named eth0.20.
admin@example:/> configure
admin@example:/config/> edit interface eth0.20
admin@example:/config/interface/eth0.20/> show
type vlan;
vlan {
tag-type c-vlan;
id 20;
lower-layer-if eth0;
}
admin@example:/config/interface/eth0.20/> leave
The tag-type defaults to c-vlan (802.1Q customer VLAN, EtherType 0x8100).
Set to s-vlan (802.1ad service VLAN, EtherType 0x88A8) to terminate an outer
S-Tag.
Tip
If you name your VLAN interface
foo0.NorvlanN, whereNis a number, the CLI infers the interface type automatically. Otherwise the type must be set explicitly.
On Top of a Bridge
When the lower-layer interface is a VLAN-filtering bridge, the VLAN interface
gives the CPU an IP-addressable endpoint inside the bridged broadcast domain
for that VID. This pattern is named vlanN by convention.
admin@example:/> configure
admin@example:/config/> edit interface vlan10
admin@example:/config/interface/vlan10/> set vlan id 10
admin@example:/config/interface/vlan10/> set vlan lower-layer-if br0
admin@example:/config/interface/vlan10/> leave
The bridge br0 must have VLAN 10 configured with the bridge itself as a
tagged member. See VLAN Filtering Bridge
for the bridge-side configuration.
Stacked (Q-in-Q)
VLAN interfaces can be stacked. A VLAN interface whose lower-layer is itself a VLAN interface terminates the inner tag, leaving the outer tag for the parent to handle.
admin@example:/> configure
admin@example:/config/> edit interface eth0.10
admin@example:/config/interface/eth0.10/> set vlan tag-type s-vlan
admin@example:/config/interface/eth0.10/> leave
admin@example:/config/> edit interface eth0.10.20
admin@example:/config/interface/eth0.10.20/> show
type vlan;
vlan {
tag-type c-vlan;
id 20;
lower-layer-if eth0.10;
}
admin@example:/config/interface/eth0.10.20/> leave
The summary view shows each VLAN row pointing at its immediate parent:
admin@example:/> show interface
INTERFACE PROTOCOL STATE DATA
eth0.10 vlan UP vid: 10
│ ipv4 10.0.10.1/24 (static)
└ eth0
eth0.10.20 vlan UP vid: 20
│ ipv4 10.0.10.20/28 (static)
└ eth0.10