Network question - disable access to an IP without running ifdown ?

[CS_DBA]

Hi All;

we have a failover tool (for a database) that pings te master and if 
it's not responding runs ifdown over ssh to bring an ip alias down, then 
runs ifup of the alias on the standby node.

A possible issue would be if the master was not reachable, thus the 
ifdown fails and once the master becomes available again then we have 2 
nodes with the ip alias and we risk a split brain issue

Is there a way to disable any traffic from getting to the old master via 
commands we can run outside of the master server?

Thanks in advance