CompTIA Network+ (N10-009)Network TroubleshootingMedium
A network technician is setting up VLANs on a new switch. After configuring VLAN 10 for the sales department and VLAN 20 for the marketing department, users in VLAN 10 can communicate with each other, and users in VLAN 20 can communicate with each other. However, users in VLAN 10 cannot access resources in VLAN 20, and vice versa. What is the MOST likely missing configuration?
- ASpanning Tree Protocol (STP) configuration.
- BDynamic Host Configuration Protocol (DHCP) server.
- CInter-VLAN routing.
- DLink Aggregation Control Protocol (LACP).
Show answer & explanationAnswer & explanation
Correct answer: C. Inter-VLAN routing.
VLANs segment a network into separate broadcast domains, preventing direct communication between them by default. To allow devices in different VLANs to communicate, an inter-VLAN routing mechanism (like a router-on-a-stick or a Layer 3 switch) must be configured.
Why the other options are wrong
- A. STP prevents loops within a single broadcast domain or between switches, it doesn't enable communication between different VLANs.
- B. A DHCP server provides IP addresses; its absence would prevent any IP communication, not just inter-VLAN. Also, intra-VLAN communication is working, implying IPs are assigned.
- D. LACP bundles multiple physical links into a single logical link for redundancy and increased bandwidth; it does not enable communication between different VLANs.
Inter-VLAN Routing
The process of forwarding network traffic between different Virtual Local Area Networks (VLANs).
- Required for devices in separate VLANs to communicate.
- Implemented using a Layer 3 switch (SVI) or a router (router-on-a-stick).
- Each VLAN needs its own IP subnet and a default gateway configured on the routing device.
Memory trick: VLANs need a 'router' to cross the 'river'.