300-425 · Question #109
An engineer must perform an assessment of a customer LAN for a future IEEE 802.11 ac Wave 2 wireless deployment. All access switches are Fast Ethernet-capable only, and the wired infrastructure…
The correct answer is D. Replace the existing switches with mGig switches. E. Ensure that cable distances between access switches and APs are not longer than 100. Cisco 3800 Series APs have multi-gigabit (mGig) Ethernet ports, so maximizing their backhaul requires mGig-capable switches and respecting the 100-meter distance limit that CAT 6A supports for mGig speeds.
Question
An engineer must perform an assessment of a customer LAN for a future IEEE 802.11 ac Wave 2 wireless deployment. All access switches are Fast Ethernet-capable only, and the wired infrastructure between existing APs and access switches is based on the CAT 6A standard. Which two actions provide maximum support of Cisco 3800 Series access points? (Choose two)
Options
- AReplace the existing switches with gigabit switches with 10 G uplinks.
- BEnsure that cable distances between access switches and APs are not longer than 55 meters.
- CReplace the existing wiring infrastructure with the CAT-7E wiring standard.
- DReplace the existing switches with mGig switches.
- EEnsure that cable distances between access switches and APs are not longer than 100
How the community answered
(30 responses)- A7% (2)
- B17% (5)
- C7% (2)
- D70% (21)
Why each option
Cisco 3800 Series APs have multi-gigabit (mGig) Ethernet ports, so maximizing their backhaul requires mGig-capable switches and respecting the 100-meter distance limit that CAT 6A supports for mGig speeds.
Standard gigabit switches are limited to 1 Gbps per port and cannot leverage the 2.5G or 5G mGig capability of the Cisco 3800, so they do not provide maximum support.
The 55-meter distance limit applies to 10GBASE-T over CAT 6 (non-A) cabling; with CAT 6A already installed, mGig is supported at the full 100 meters, making a 55-meter restriction unnecessarily limiting.
CAT 6A already fully supports mGig speeds at the required distances; CAT-7E is not a ratified IEEE standard and replacing working CAT 6A infrastructure provides no practical benefit for this deployment.
Cisco 3800 Series APs include mGig ports supporting 100 Mbps, 1 Gbps, 2.5 Gbps, and 5 Gbps; the existing Fast Ethernet switches cap the backhaul at 100 Mbps, so replacing them with mGig switches is required to utilize the AP's full throughput capability.
CAT 6A cabling supports mGig speeds (2.5G and 5G) at distances up to 100 meters per the NBASE-T standard, so ensuring cable runs do not exceed 100 meters is the correct constraint to maintain maximum throughput on the existing CAT 6A plant.
Concept tested: Multi-gigabit infrastructure requirements for 802.11ac Wave 2 APs
Source: https://www.cisco.com/c/en/us/products/collateral/wireless/aironet-3800-series/datasheet-c78-736508.html
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