Metro Mode:
The Metro Mode is a quick configuration VLAN environment method on Port-based VLAN. It will create 6 or 7 Port-based VLAN groups.
Double-tag:
Double-tag mode belongs to the tag-based mode, however, it would treat all frames as the untagged ones, which means that tag with PVID will be added into all packets. Then, these packets will be forwarded as Tag-based VLAN. So, the incoming packets with tag will become the double-tag ones.
Fig. 3-28
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