Huawei Quidway S7700 Configuration Manual - Ethernet page 83
Smart routing switch
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- Configuration manual (833 pages) ,
- Configuration manual - multicast (551 pages) ,
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Quidway S7700 Smart Routing Switch
Configuration Guide - Ethernet
l
Issue 01 (2011-07-15)
Figure 3-3 802.1Q frame format
6bytes
6bytes
Destination
Source
address
address
2bytes 3bits
– Tag Protocol Identifier (TPID): a 16-bit field set to a value of 0x8100 in order to identify
the frame as an IEEE 802.1Q-tagged frame. If an 802.1Q-incapable device receives an
802.1Q frame, it will discard the frame.
– Priority (PRI): a 3-bit field which indicates the frame priority. The value ranges from 0
to 7. The greater the value, the higher the priority. These values can be used to prioritize
different classes of traffic to ensure that frames with high priorities are transmitted first
when traffic is heavy.
– Canonical Format Indicator (CFI): a 1-bit field. If the value of this field is 1, the MAC
address is in the non-canonical format. If the value is 0, the MAC address is in the
canonical format. CFI is used to ensure compatibility between Ethernet networks and
Token Ring networks. It is always set to zero for Ethernet switches.
– VLAN Identifier (VID): a 12-bit field specifying the VLAN to which the frame belongs.
On the S7700, VLAN IDs range from 0 to 4095. The values 0 and 4095 are reserved,
and therefore VLAN IDs range from 1 to 4094.
Each frame sent by an 802.1Q-capable switch carries a VLAN ID. On a VLAN, Ethernet
frames are classified into the following types:
– Tagged frames: frames with 32-bits 802.1Q tags.
– Untagged frames: frames without 32-bits 802.1Q tags.
VLAN division methods
Table 3-1
shows VLAN division methods.
Table 3-1 VLAN division methods
VLAN
Definition
Division
Method
Port-based
VLANs are configured based on ports on a switch. For example, ports
VLAN division
1 to 4 on a switch are added to VLAN 2; ports 5 to 8 are added to
VLAN 3.
Ports on different Ethernet switches can be added to one VLAN. For
example, ports 1 to 4 on switch A and ports 3 to 6 on switch B can
be added to the same VLAN.
Each switch maintains a VLAN mapping table that records mappings
between local ports and VLANs.
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
4bytes
2bytes
802.1Q
Length/
Type
Tag
TPID
PRI
CFI VID
1bit
12bits
3 VLAN Configuration
42-1500bytes 4bytes
Data
FCS
66
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