Layer 2 Firewall [transparent Firewalls

I have this topology

r1 ---R2 --- r3

R2 is bridging E0/0[to R1] and E0/1[to R3]. I am using IRB. with
"Bridge 1 route ip". I assign the BVI with an Ip address from the
same subnet as R1 and R3. now. i configure CBAC and put it in inbound
on E0/0 [R2] and an accesslist denying ICMP, IP, on E0/1 R2.
unfortunately there are no hits on the ACL. and CBAC isn't inspecting
the ICMP inbound on R2's E0/0. Is it a requirement for them to RUN
dot1q encapsulation for l2firewall to work? . the connections in my
diagram, there's no switches involved. hence no trunking?

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