However, Cisco Catalyst
switch ports run DTP by default, which tries to automatically negotiate a trunk link. This
Cisco proprietary protocol can determine an operational trunking mode and protocol on a
switch port when it is connected to another device that is also capable of dynamic trunk
negotiation. Table 2-15 outlines DTP mode operations.
VLANs and IP Subnets
Each VLAN will correspond to a unique IP subnet. Two devices in the same VLAN should
have addresses in the same subnet. With intra-VLAN traf?¬?c, the sending device recognizes
the destination as local and sends an ARP broadcast to discover the MAC address of the
destination.
Two devices in different VLANs should have addresses in different subnets. With inter-
VLAN traf?¬?c, the sending device recognizes the destination as remote and sends an ARP
broadcast for the MAC address of the default gateway.
Inter-VLAN Connectivity
Most of the time, inter-VLAN connectivity issues are the result of user miscon?¬?guration.
For example, if you incorrectly con?¬?gure a router on a stick or Multilayer Switching (Cisco
Express Forwarding), then packets from one VLAN may not reach another VLAN.
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