请问18-21a这个可以做流量限制吗

可以做针对网段的流量限制.

用qos命令来做.

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qos carl 1 source-ip-address range 192.168.1.3 to 192.168.1.100 per-address
qos carl 2 destination-ip-address range 192.168.1.3 to 192.168.1.100 per-address

interface Ethernet1/0
ip address 192.168.1.1 255.255.255.0
qos car inbound carl 1 cir 64000 cbs 64000 ebs 64000 green pass red discard
qos car outbound carl 2 cir 100000 cbs 100000 ebs 100000 green pass red discard

上面的代码就是使用方法.