When the UE attaches to LTE network, an IP address is allocated to the UE by PGW to make easy data connectivity between the UE and Packet Data Network. More than one PGW might be exist in the network, and consequently the UE may set up PDN connections with more than one PGW and may be assigned to more than one IP address (different IP address by different PGW). First IP address which is assigned to the UE by a PGW during initial attach, it stays with the UE as long as the UE is attached to the LTE network.
There are two kinds of IP allocation: dynamic and static: Dynamic IP allocation is assigned to the UE in every attach request, PGW takes a random IP address from the network IP pool. In static IP allocation scenario, PGW allocates a designated IP address to UE upon its subscription, and then allocates the designated IP address every time it accesses the network.
* Note: PGW: Packet Data Network Gateway or PDN Gateway