Exam 300-425 topic 1 question 185 discussion

Actual exam question from Cisco's 300-425

Question #: 185
Topic #: 1

A network engineer must design a new wireless solution for a company, but the budget can only stretch to include a single Cisco 9800-40 WLC. The company requires high availability between the WLC and the core switch in the event of a cable failure. The WLC must dynamically manage port redundancy and perform load balancing between APs transparently. Which design approach must the engineer take to meet the requirements?

A. LAG
B. Multi-LAG
C. LACP
D. PAgP

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Suggested Answer: A 🗳️

by Lakshan__97 at June 6, 2024, 1:21 p.m.

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zyxzyx123

9 months, 1 week ago

A link aggregation group (LAG) bundles all of the controller’s distribution system ports into a single 802.3ad port channel. This reduces the number of IP addresses required to configure the ports on your controller. When LAG is enabled, the system dynamically manages port redundancy and load balances access points transparently to the corresponding user. https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/17-9/config-guide/b_wl_17_9_cg/m_lacp_pagp.html

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Farhad123

9 months, 3 weeks ago

Link Aggregation Group (LAG) allows multiple physical ports to be combined into a single logical channel. In the scenario where only one Cisco 9800-40 WLC is available and high availability is required, LAG can be used to manage port redundancy and perform load balancing between APs transparently. This ensures that if one cable fails, the others can continue to carry the traffic without any perceived downtime.

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Lakshan__97

1 year ago

Selected Answer: A

Be aware that even though the LAG acts as a traditional EtherChannel, Cisco WLCs do not support any link aggregation negotiation protocol, like LACP or PAgP, at all. Therefore, you must configure the switch ports as an unconditional or always-on EtherChannel.

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zyxzyx123

9 months, 1 week ago

Incorrect - AIROS only support "on mode", but a 9800 like the question here WLC supports LACP: "LACP is supported on a standalone controller from Cisco IOS XE Gibraltar 16.12.x release. LACP is supported on an SSO pair from Cisco IOS XE Amsterdam 17.1.1s onwards." So is PAgP for that matter. Since multi lag is mentioned, then one could conclude that the version here is at least 17.2.1: "From Cisco IOS XE Amsterdam 17.2.1, Multichassis Link Aggregation Group (multi-LAG), which provides flexibility in connecting the controller to a switch's infrastructure is supported. " https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/17-9/config-guide/b_wl_17_9_cg/m_lacp_pagp.html

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Farhad123

9 months, 3 weeks ago

the right statement is : Be aware that even though the LAG acts as a traditional EtherChannel, AireOS-based WLCs do not support any link aggregation negotiation protocol, like LACP or PAgP, at all. Therefore, you must configure the switch ports as an unconditional or always-on EtherChannel. You can configure and verify the LAG mode by going to Controller > General > LAG Mode on next reboot.

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