In the static cellular interface IPv4 mode of operation, the unnumbered interface configured under the PDN router interface is a loopback interface that is assigned a static address on the associated cellular port. This statically assigned IP address does not match the system IP address, which is a private address. When the cellular port associated with the PDN interface attaches to the cellular network, the cellular network assigns the same static IP address to the cellular port as the address assigned to the loopback address under the PDN router interface.
The cellular IP address assigned to the PDN router interface never changes after each subsequent cellular attachment. The static address assigned during the PDN attachment process is then used as the PDN router interface IP address for services operation. The PDN router interface is declared operationally up only when the PDN attachment completes and the IP address assigned by the cellular network matches the PDN router interface loopback address. If the address is not the same, the PDN interface stays operationally down and an alarm is raised.
The CLI output below shows an example of a PDN interface configured for static cellular interface IPv4 mode.
*A:DUT# config# router
interface "pdn-loopback"
address 88.0.0.1/32
loopback
no shutdown
exit
interface "pdn1-sim1" pdn
port 1/1/1
unnumbered "pdn-loopback"
no shutdown
exit
exit
exit
When operating in static cellular interface IPv4 mode, consider the following points.
Some wireless service providers require that all packets entering their network from UE attached to their network have a source IP address that matches the IP address that the cellular network assigned to the UE. When this is a requirement and the node is using static cellular interface IPv4 mode, the PDN interface must be configured with an IP filter that allows only egress packets that have a source IP address that matches the IP address that was assigned during the PDN attachment. A filter must be configured on each PDN router interface that requires filtering.
The system IP address used by the NSP NFM-P to manage the node is a private IP address. An in-band management VPRN service is required for the NSP NFM-P to reach the node.