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We have 3750g, 3750e, 4948, 2960 series Cisco switches and all of them are 48 ports so we want to create one standard access list per port switch and in every ACL we permit 5-6 prefix (short prefixes like /28 or /29) and deny other IP addresses, so if I have 38-40 ACLs for 38-40 ports, will this cause high CPU usages on my switches or not?

Thank you.

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    Dec 25, 2018 at 9:37
  • Can I ask why you want to do this? What's the reasoning behind it?
    – Jesse P.
    Jan 2, 2019 at 4:47

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No, at least not usually. ACLs in switches use ternary content-addressable memory (TCAM) and don't use the CPU at all.

While ACLs do use up some resources, this number of ACEs doesn't usually impact the forwarding speed (at least not significantly, depending on the switch at hand).

Using large numbers of entries (many 100) may require multiple check cycles on some switches, so to make sure you'll need to check the specifications.

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