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{ "lLangCode": "en", "lName": "English", "lCountryCode": "us", "transcode": "en_US" }
English
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Effect of Two-Color Policers on Shaping Rate Changes

date_range 13-Jan-21

When you configure a change in shaping rate, it is important to consider the effect on the bandwidth limit. Whenever the shaping rate changes, the bandwidth limit is adjusted based on whether a logical interface (unit) or bandwidth percentage policer is configured.

When a logical interface bandwidth policer is configured, the order of priority for the shaping rate (if configured at that level) is:

  • The shaping rate applied to the logical interface (unit).

  • The shaping rate applied to the physical interface (port).

  • The physical interface speed.

When a bandwidth percentage policer is configured, the order of priority for the shaping rate (if configured at that level) is:

  • The shaping rate applied to the physical interface (port).

  • The physical interface speed.

These guidelines must be kept in mind when calculating the logical link speed and link speed from the configured shaping rate, which determines the rate-limited bandwidth after the policer is applied.

In the following configuration, for example, a shaping rate has been configured for the logical interface, but a bandwidth percentage policer is also configured and applied to the same logical interface. Therefore policing is based on the physical interface speed of 1 Gbps.

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[edit interfaces]
ge-0/1/0 {
    per-unit-scheduler;
    vlan-tagging;
    unit 0 {
        vlan-id 1;
        family inet {
            policer {
                output policer_test;
            }
            address 10.0.7.1/24;
        }
    }
}

[edit firewall]
policer policer_test {
    if-exceeding {
        bandwidth-percent 75;
        burst-size-limit 256k;
    }
    then discard;
}

[edit]
class-of-service {
    interfaces {
        ge-0/1/0 {
            unit 0 {
                shaping-rate 15m;
            }
        }
    }
}
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