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Details about the devices

We have a 24 port NETGEAR managed POE switch that has QoS capabilities.

We also have the following unmanaged switches, 24 port Cisco POE, 48 port Cisco, 48 port NETGEAR, and 24 port tp-link.

Question

If any of the unmanaged switches are between the managed switch and the NETGEAR router (to be replaced by a Ubiquiti EdgeRouter 4) will that make the QoS on the managed router completely pointless?

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    As per your links, Those switches are managable. – infra May 16 at 5:54
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    I don't know about NETGEAR, But Cisco 2960 is manageable switch – infra May 16 at 6:27
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    Cisco only makes managed switches. They sold off the third party companies making their consumer market switches. The Cisco 2960 is very much manageable and can provide many features, including QoS. Remember, that QoS only benefits, when a link is congested. – user56700 May 16 at 6:30
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    It depends on which QoS you mean. DSCP is on the layer-3 packets, and switches will ignore that. The CoS on a trunk will be honored because a trunk can only be configured on a managed switch, and CoS is part of the 802.1Q frame tag for a trunk. – Ron Maupin May 16 at 14:28
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The 2960 series is managed. Even the Netgear GS348 supports some QoS (its flavor of, check the documentation).

QoS prioritizes traffic - forward important frames, drop less important frames - when that becomes necessary due to link overload = congestion. If none of your links is supposed to handle more traffic then it is capable of, there's no congestion, and no real need for QoS.

So, if those switches where congestion is possible or most likely to happen support QoS features and are configured appropriately, you're basically good. Without deep insight into your network - topology, device configurations, (peak) workloads and flow patterns etc your question cannot be really answered.

Do unmanaged switches honour QoS priorities set by managed switches?

Some do, many don't. Since you cannot configure their QoS features you have to make do with what's there. Some switches may support L2 priorities (priority code points from 802.1p/q), others may support differential services (DSCP) from the L3 IP packets.

You need to make sure that upstream, managed switches set/use the QoS flags that the downstream, unmanaged switches require. Since that can get very hard it's easiest to use managed switches with a common logic (mostly from the same vendor/series).

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