Does IPv6 migration of UEs and PDN Gateway require any support from eNodeBs? eNodeB, MME, HLR, AAA and SGW need not be upgraded immediately along with PDN gateway to support Ipv6 external connectivity to the UEs.
eNodeBs communicate with the other 3GPP network elements for signaling and transporting the UE traffic over GTP tunnel. They relay traffic from PDCP layer to the GTP tunnels and vice versa. As such they don't look deep into the data as such. It could be IPv4 or Ipv6 packet. GTP layer in eNodeB is expected to pick up the data, snap the GTP-U/UDP/IP header and send it over to the SGW by securing with IPsec. GTP-U can use IPv4 connectivity to talk to SGW and eNBs etc.. Similarly signaling communication can happen on Ipv4 network.
PDCP RoHC (Robust Header Compression) is the only mandatory component in the eNodeB which tried to interpret the packets to/from UEs. I believe the first generation of eNBs would expect PDCP RoHC to support both IPv4 and IPv6. Some eNBs have some sophisticated functionality such as 'Application Detection'. Any component that interprets the user traffic would need to have IPv6 intelligence. I believe eventually all the components such as GTP-U, IPsec, QoS require IPv6 support as operators move to IPv6 only networks.
By the way, I saw one IETF draft on IPv6 in 3GPP EPS. Please find it here.