Question: In PMIPv6 mode, when a UE requests DNS IPv4/IPv6 address during IPsec tunnel establishment, how does an ePDG that supports Additional Protocol Configuration Options IE handle this request?
Option 1: The ePDG ignores the request and proceeds with the default DNS configuration.
Option 2: The ePDG includes the DNS IPv4/IPv6 Server Address Request parameter in the PBU to the PDN-GW but does not await a response.
Option 3: The ePDG includes the Additional Protocol Configuration Options IE with 'DNS Server IPv4/v6 Address' parameter in the PBU to the PDN-GW and sends the received DNS information in the CFG_REPLY to the UE if available.
Option 4: The ePDG denies the IPsec tunnel establishment due to lack of support for DNS requests over PMIPv6.
Explanation: This option correctly describes the procedure for handling UE requests for DNS IPv4/IPv6 addresses during IPsec tunnel setup in PMIPv6 mode. The ePDG facilitates this by including the relevant parameter in the PBU to the PDN-GW and relaying the received DNS information back to the UE in the CFG_REPLY, enabling the UE to configure its DNS settings appropriately within the PMIPv6 framework for UEs connecting via untrusted networks through the ePDG.