some document to read

https://supportforums.cisco.com/document/59741/asr9000xr-flexible-vlan-matching-evc-vlan-tag-rewriting-irbbvi-and-defining-l2
http://www.cisco.com/c/en/us/support/docs/routers/asr-9000-series-aggregation-services-routers/116453-technote-ios-xr-l2vpn-00.html
http://www.cisco.com/c/en/us/support/docs/routers/asr-9000-series-aggregation-services-routers/116500-problemsolution-product-00.html