County jail IT places the parks VLAN gateway as the first usable address in 10.40.12.0/28. Which address should be configured on the SVI?
Select an answer to reveal the explanation.
Short Explanation
In a /28, .0 is the network ID and .15 is broadcast — neither is a happy home for a gateway. First usable is .1, which is the usual municipal SVI pick for that tiny parks block.
Full Explanation
County jail IT places the parks VLAN gateway as the first usable address in 10.40.12.0/28. A /28 has 16 addresses: network ID 10.40.12.0, usable hosts 10.40.12.1 through 10.40.12.14, and broadcast 10.40.12.15. The first usable address is therefore 10.40.12.1, which is the conventional municipal SVI/gateway choice when the plan specifies “first usable.” Configuring the SVI with that address keeps host default gateways simple and matches the documented addressing standard.
10.40.12.0 is the network identifier and must not be assigned to an SVI as a host address. 10.40.12.15 is the directed broadcast for the /28 and likewise is not a valid unicast gateway. 10.40.12.16 falls outside 10.40.12.0/28 entirely (it begins the next /28, 10.40.12.16/28), so parks hosts using a /28 mask would not treat it as on-link.
Exam caveat: “first usable” means the first address after the network ID, not the network ID itself and not the broadcast. Always derive usable range from prefix length before picking gateway, HSRP VIP, or DHCP exclusions.
Operational check: on the parks SVI, set 10.40.12.1/28, exclude .1 from DHCP if used, point a test parks host gateway to .1, and verify ARP resolution and ping to the SVI. Confirm show interfaces vlan / ip brief shows .1 and that no device mistakenly uses .0 or .15.