Egress vlan tag question

hi,

im doing intervlan routing on my switch without using bridging.
what does this command actually do?

egress-vlan-tag add tagged-ports=switch1-cpu vlan-id=20

Routing in a CRS requires the use of the CPU. When you put a subnet on a vlan, the only way to route that traffic between vlans or out of the CRS is to tag it to the CPU for the routing process.