NEO Training Center | Học CCNA tốt nhất – Vlans
NORMAL & EXTENDED VLANS
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Due to different historical implementations of VLANs on Cisco switching platforms, some VLANs are referred to as normal, while others are consideredextended. VLANs are generally a simple concept, but how and where they implemented depends on several factors – including the numerical range they fall within.

Normal Range VLANs

Simply put, normal range VLANs are VLANs 1-1005. Normal range VLANS can be configured in both database configuration mode and global configuration mode and are stored in vlan.dat file in Flash memory. VTP versions 1 and 2 can advertise normal range VLANs only.

Extended Range VLANs

Extended VLANs are numbered 1006-4094 and are often used in large enterprise environments or by service providers who provision thousands of customer networks. These are not stored in the vlan.dat file in Flash when running VTP versions 1 or 2 and are not advertised. If a switch is running VTPv1 or VTPv2, the switch must be in transparent mode to even configure extended range VLANs. As such, extended VLANs can not be configured using VLAN database mode (only configuration mode) and will be saved in the configuration file only.

VTP version 3 supports the use of extended range VLANs natively and will advertise both normal and extended ranges. VTPv3 also stores all VLANs (including extended) in the vlan.dat Flash file.

802.1Q and ISL Trunking Support

Modern implementations of both 802.1Q and Cisco’s proprietary ISL trunking protocols support extended range VLANs. Initially, ISL only supported normal range VLANs, but more recent versions of IOS support trunking extended range VLANs.

The table below outlines normal and extended VLAN uses as well as VTP version 1 and 2 support.

VLANs

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