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802.1q and ISL trunks
Cisco Hands On Training Podcast
English - February 24, 2009 02:17 - ★★★★ - 72 ratingsTechnology Education How To cisco ccie rip ospf bgp ccna ccnp Homepage Download Apple Podcasts Google Podcasts Overcast Castro Pocket Casts RSS feed
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Switches can have multiple vlans. When we connect switches together we use 802.1q trunks (or older ISL trunks) to run multiple vlans over one physical link. With either trunking protocol, a tag is added to the ethernet frame with the vlan information. ISL is an older Cisco-proprietary trunking protocol. Newer switches do not even support ISL. Newer switches use the 802.1q vendor-indepentend trunking protocol. Cisco switches also speak the dynamic trunk protocol (DTP) to dynamically negotiate whether to enable a trunk.