Allied Telesis x908 - Manual (Page 10)

Page 10 | AlliedWare Plus™ OS How To Note
Making filters by using QoS class-maps
Matching on “inner” keywords for nested VLANs
The match tpid, match inner-tpid, match inner-vlan, and match inner-cos
commands all apply to nested VLAN configuration. In this situation, the packets arriving at
the core-facing port can have two VLAN tags configured on them.
z The match tpid command matches on the first Tag Protocol Identifier field in the packet.
z The match inner-tpid command matches on the TPID in the second 802.1Q tag in the
packet.
z The match inner-vlan command matches on the tunnelled VLAN ID in the second
802.1Q tag in the packet.
z The match inner-cos command matches on the 802.1P field in the second tag in the
packet.
The following table shows where in the packet the inner and outer tags will be matched.
Some important points to keep in mind while configuring the “inner” commands are:
z When packets arrive at a customer port of a nested VLAN, the command match vlan
will match the VID of the nested VLAN that the port is a member of, which is just how
this command normally operates.
z When packets arrive at a customer port of a nested VLAN, the “inner” commands will
match the attributes of the first tag in the packets. This is because when the packet is
forwarded from the core port, that first tag will have become the inner tag. So, from the
point of view of the nested VLAN, the tag that is on the packet when it arrives into the
customer port is the inner tag.
z When nested VLANs are disabled, and “inner” commands have been configured in class-
maps, these parameters will be applied as though all packets arriving at the switch were
double tagged. In other words, there will be no attempt to make a distinction between
“customer” and “core” ports. So, if the packets arriving at the switch are not double
tagged, then the “inner” commands will just match on whatever data happens to be in the
packets at the position where an inner tag would have been.
Therefore, when you disable nested VLANs, you should also remove the match
commands.
z When nested VLANs are being used, the commands match tpid and match cos cannot
be used in class-maps applied to customer ports.
z If you attach the class-map to a number of ports, they will all be treated like core ports if
at least one of the ports is a core port.
Outer VLAN parameters
(normal)
Inner VLAN parameters
Customer port VLAN 1st tag
Core port 1st tag 2nd tag
Nested VLANs disabled 1st tag 2nd tag