The following test was run on a QNX 7.0 VM:

# ifconfig
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 33136
        inet 127.0.0.1 netmask 0xff000000
        inet6 ::1 prefixlen 128
        inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
vx0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        capabilities rx=1f<IP4CSUM,TCP4CSUM,UDP4CSUM,TCP6CSUM,UDP6CSUM>
        capabilities tx=7e<TCP4CSUM,UDP4CSUM,TCP6CSUM,UDP6CSUM,TSO4,TSO6>
        enabled rx=1f<IP4CSUM,TCP4CSUM,UDP4CSUM,TCP6CSUM,UDP6CSUM>
        enabled tx=7e<TCP4CSUM,UDP4CSUM,TCP6CSUM,UDP6CSUM,TSO4,TSO6>
        address: 00:0c:29:89:ba:cd
        media: Ethernet autoselect
        status: active
        inet 192.168.36.129 netmask 0xffffff00 broadcast 192.168.36.255
        inet6 fe80::20c:29ff:fe89:bacd%vx0 prefixlen 64 scopeid 0x11
# 
# ifconfig vx0 alias 192.168.36.140/24
ifconfig: SIOCAIFADDR: File exists
# 
# route show
Routing tables

Internet:
Destination        Gateway            Flags 
default            192.168.36.2       UG     
localhost.localdom 127.0.0.1          UH     
192.168.36.0/24    link#17            U      
192.168.36.1       00:50:56:c0:00:08  UHL    
192.168.36.2       00:50:56:ec:93:26  UHL    
server0.training.l 127.0.0.1          UGH    

Internet6:
Destination        Gateway            Flags 
localhost.localdom localhost.localdom UH     
fe80::%lo0         fe80::1%lo0        U      
fe80::1%lo0        link#1             UHL    
fe80::%vx0         link#17            U      
fe80::20c:29ff:fe89:bacd%vx0 00:0c:29:89:ba:cd  UHL    
ff01:1::           localhost.localdom U      
ff01:11::          link#17            U      
ff02::%lo0         localhost.localdom U      
ff02::%vx0         link#17            U      
# 
# ifconfig vx0 alias 192.168.36.140/32
# 
# ifconfig
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 33136
        inet 127.0.0.1 netmask 0xff000000
        inet6 ::1 prefixlen 128
        inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
vx0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        capabilities rx=1f<IP4CSUM,TCP4CSUM,UDP4CSUM,TCP6CSUM,UDP6CSUM>
        capabilities tx=7e<TCP4CSUM,UDP4CSUM,TCP6CSUM,UDP6CSUM,TSO4,TSO6>
        enabled rx=1f<IP4CSUM,TCP4CSUM,UDP4CSUM,TCP6CSUM,UDP6CSUM>
        enabled tx=7e<TCP4CSUM,UDP4CSUM,TCP6CSUM,UDP6CSUM,TSO4,TSO6>
        address: 00:0c:29:89:ba:cd
        media: Ethernet autoselect
        status: active
        inet 192.168.36.129 netmask 0xffffff00 broadcast 192.168.36.255
        inet alias 192.168.36.140 netmask 0xffffffff broadcast 192.168.36.140
        inet6 fe80::20c:29ff:fe89:bacd%vx0 prefixlen 64 scopeid 0x11
# 
# route show
Routing tables

Internet:
Destination        Gateway            Flags 
default            192.168.36.2       UG     
localhost.localdom 127.0.0.1          UH     
192.168.36.0/24    link#17            U      
192.168.36.1       00:50:56:c0:00:08  UHL    
192.168.36.2       00:50:56:ec:93:26  UHL    
server0.training.l 127.0.0.1          UGH    
192.168.36.140/32  link#17            U      

Internet6:
Destination        Gateway            Flags 
localhost.localdom localhost.localdom UH     
fe80::%lo0         fe80::1%lo0        U      
fe80::1%lo0        link#1             UHL    
fe80::%vx0         link#17            U      
fe80::20c:29ff:fe89:bacd%vx0 00:0c:29:89:ba:cd  UHL    
ff01:1::           localhost.localdom U      
ff01:11::          link#17            U      
ff02::%lo0         localhost.localdom U      
ff02::%vx0         link#17            U      
#