When the Cisco Integrated Communications System (ICS) 7750 system cards are moved out from the default native VLAN (VLAN 1) to any other VLAN, the ICS 7750 does not discover the System Processing Engine (SPE).
The ICS 7750 System Manager discovers all the system cards using Cisco Discovery Protocol (CDP) in VLAN 1. ICS software versions 2.5 and 2.6 have limited VLAN capabilities. All of the system cards in the chassis must be on the native VLAN (typically VLAN 1), which uses untagged frames. If not, the system discovery fails. To resolve the issue, all the system cards that are moved out of native VLAN should be connected back in VLAN 1.