I'm newby in configuring EFP on ASR series. So after rereading the manuals I cannot understand how trunk EFP service instance recognize what TAG must be imposed on frame. Part of initials configuration:
no ip address
service instance 10 ethernet
encapsulation dot1q 10
bridge-domain 30 ! bridge-domain will be S-Tag on trunk port
service instance 11 ethernet
encapsulation dot1q 11
bridge-domain 40 ! bridge-domain will be S-Tag on trunk port
no ip address
service instance trunk 1 ethernet
encapsulation dot1q 30-40 ! in this case, we only need vlan 30 and 40
rewrite ingress tag pop 1 symmetric
bridge-domain from-encapsulation ! outer vlan tag is used as bridge-domain
Manuals say that on ingress (G0/1/0) frame will be (in this particular case) sent to bridge-domain 30 or 40 based on incoming tag 10 or 11 beeing untouched. Ok. It is unclear how trunk EFP become member of 30-40 b/d, but let suppose that "bridge-domain from-encapsulation" statement force this in such a way that frames with tags 10 or 11 directed to G0/1/2.
On egress (G0/1/2) what statement forces specific tag (10 or 11) to be prepended with either 40 or 30 S-tag? Either frames will egress G0/1/2 with its "native" tag (10 or 11). That is why Q arise, because manuals say that only relevant in this case statement "bridge-domain from-encapsulation" behavior is to define what bridge-domain frame will enter on ingress (G0/1/2 in this case) based on outer tag! :O)
Can anybody explain me, is this also extended undocumented influence of "bridge-domain from-encapsulation" to egress direction?