Westermo U200 Operator manal - Manual (Page 31)

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Figure 12 shows the VLAN dialog setup of the IP configuration tool.
The VLAN implementation is meant for both Ethernet end nodes that support tagging and for
those that do not. An Ethernet end node that are not able to send tagged packets can,
however, only participate in one of the “Standard VLANs”, i.e. the default VLAN id for the port
is used as the VLAN for such an end node. A default VLAN id for a given port will be
associated to each untagged packet received on the switch (or tagged packet with VLAN id
equal to 0). This VLAN id will be added to packet as an IEEE802.1Q tag. This tag can be
removed at the output port(s) if the port(s) is configured for tag removal.
Seven different “Standard VLANs” are available:
- White, VLAN id = 1, priority = 7 [high]
- Red, default VLAN id = 2, default priority = 0 [low]
- Blue, default VLAN id = 3, default priority = 0 [low]
- Green, default VLAN id = 4, default priority = 0 [low]
- Yellow, default VLAN id = 5, default priority = 0 [low]
- Brown, default VLAN id = 6, default priority = 0 [low]
- Pink, default VLAN id = 7, default priority = 0 [low]
The VLAN that is selected as the default VLAN for a given port will appear as an
unchangeable VLAN, while other VLANs selected for the same port has only relevance in
case the end node connected to the same port is able to send and receive packets with these
VLAN ids.
All ports on a switch are by default members of the white VLAN, i.e. the switch management
VLAN. The administrator can remove non-trunk ports from the white VLAN. That means that
such ports cannot be used for switch management. All trunk ports are part of the white VLAN.
This is automatically configured on run-time.
Port 1 has the white VLAN id as the ports default VLAN id, and this cannot be changed. An
end node that is used for network management (SNMP or IP configuration) must always use
the white VLAN in order to communicate with the switch CPUs. Thus, the switch CPUs can
always be accessed via port 1 with untagged packets, since port 1 has the white VLAN as the
default VLAN.
The tag is not removed on packets sent on a trunk port, and each trunk port is member of all
the seven “Standard VLANs” and the four “Additional VLANs”. This means that the user does
not need to set any VLAN parameters on the trunk ports, and that any network topology
change will be handled automatically.
The layer 2 priority of a given VLAN can also be set. I.e.:
- Priority 0 ..3: low priority
- Priority 4 ..7: high priority
This priority will be added to the tag. See Figure 8 for the MAC header with tag.
The legal VLAN id range is [1 .. 4096]. A few VLAN ids in this range are reserved for other
use. These ids can not be set in the IP configuration tool.
The network should only be based on switches enabled for VLAN or not. A mix of switches
with and without VLAN support will not provide the user with the capability of tag removal on
all parts of the network.
11.1 Standard vs. Additional VLANs