To perform redundant switching more easily and speedily without updating an ARP (Address Resolution Protocol) table.

A DCME (Digital Circuit Multiplication Equipment) system 30 is equipped with: three in-use systems DCME 31 to DCME 33 actualizing the same function; a console 36 which outputs a switching instruction when informed of fault occurrence from an abnormal in-use system DCME among the three in-use systems DCME 31 to DCME 33; and one standby system DCME 34 which is a DCME used as an alternative device for the in-use system DCME and equipped with a switching notification means of obtaining control information regarding the communication operation of the abnormal in-use system DCME from the console 26 in response to the switching instruction and sending a generated redundant switching message to the communication destination of the abnormal in-use system DCME.