Alloy Computer Products GSM-8T16SFP - Manual (Page 63)

GSM Series User Manual
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Alloy Computer Products Pty Ltd Copyright ©2006
two VLAN groups. The switch has support for up to 24 port-based VLAN groups.
Tag-based:
Tag-based VLAN’s identify members by its VID. A VID can be applied to a packet
from a host machine that supports 802.1q or from the switch itself when a packet
is sent from the switch. Ingress and Egress rules can also be applied to each
port to identify how a packet is handled. The switch will accept both tagged and
un-tagged packets depending on the ingress rules that have been defined. Rules
can be created to allow only incoming packets to be tagged; however when this
Rule is applied any untagged packets will be dropped.
Each tag-based VLAN you build must have a VLAN name and VLAN ID. Valid
VLAN ID’s range from 1 – 4096. The maximum number of tag-based VLAN
groups that can be created is 64.
Metro Mode:
Metro mode is a quick and easy configuration of port-based VLAN’s. Metro mode
quickly separates the switch into 14 or 15 (GSM-16T2SFP) 23 or 24 (GSM-
24T2SFP, GSM-8T16SFP) port-based VLAN groups. All ports on the switch are
configured into separate VLAN groups and can not communicate with each
other. Depending on the way it is configured all ports will be able to communicate
with one or two uplink ports and will not be able to communicate with each other.
Double-tag:
Double-tag mode belongs to tag-based VLAN’s; however it treats all packets as
untagged packets. This means that a tag with a pre-defined PVID will be added
to all packets. Therefore all packets that leave the switch will be tagged, if a
tagged packet is received by the switch an additional tag will be added thus
becoming a double-tag packet.
Double tag (Q in Q) provides additional flexibility for managing traffic flows, using
this method, service providers could use, for example, sending one flow of data
to a building and then separate and forward traffic based on supplemental IDs
used to identify specific tenants in a site. This can be useful for situations in
which traffic must be separated for management, tracking and billing purposes.
In addition this method enables customers to maintain their desired tag, without
concern that other organisations will share the same ID. Service providers avoid
potential problems by simply adding a second ID per customer in addition to the
shared tag.