
User’s Manual of LRP-822CS/LRP-1622CS
120
nabled will put the VID number, priority and other VLAN information into the
header of all packets that flow into those ports. If a packet has previously been tagged, the port
will not alter the pa
ping the VLAN information intact. The VLAN information in the
can then be us
the network to make
t-forwarding
ntaggi
ackets that flow into those
ports. If the packet doesn't have an 802.1Q VLAN tag, the port will not alter the packet. Thus,
all packets received by and forwarded by an untagging port will have no 802.1Q VLAN
information. (Remember that the PVID is only used internally within the Switch). Untagging is
ets from an 802.1Q-compliant network device to a non-compliant network
device.
Tagged:
Ports with tagging e
cket, thus kee
tag
ed by other 802.1Q compliant devices on
packe
decisions.
Untagged:
Ports with u
ng enabled will strip the 802.1Q tag from all p
used to send pack
Frame Income
Frame Leave
Income Frame is
tagged
Income Frame is
untagged
Leave port is tagged
Frame remains tagged
Tag is inserted
Leave port is untagged
Tag is removed
Frame remain untagged
Table 4-5-1:
Ingress / Egress Port with VLAN VID Tag / Untag Table
■
IEEE 802.1Q Tunneling (Q-in-
) is desig
affic for multiple customers across their networks.
maintain cus
nfigurations even when different customers
use the same internal VLAN IDs. This is accomplished by inserting
Service Provider VLAN (SPVLAN)
tags into the customer’s
r
e service provid
ags when the frames leave the network.
A service provider’s customers may ha
cific requ
IDs and number of VLANs supported.
VLAN ranges required by different customers in the same service-provider network might easily overlap, and traffic passing
h the infrastructure might be mixed. Assigning a unique range of VLAN IDs to each customer would restrict customer
urations, require intensive processing of VLAN mapping tables, and could easily exceed the maximum VLAN limit of
Q)
IEEE 802.1Q Tunneling (QinQ
ned for service providers carrying tr
QinQ tunneling is used to
tomer-specific VLAN and Layer 2 protocol co
f ames when they enter th
er’s network, and then stripping the t
ve spe
irements for their internal VLAN
throug
config
4096.