Network utilization maxed out during backup. Is it bad in itself?

We have a cluster of two Oracle DBs. Monitoring software agent is installed on both of the machines and overnight, when backups are happening, we get warnings that network interface utilisation on the servers is above 90% - I'm sure it gets maxed out. Is this an issue or do you, experienced DBAs, allow the DB servers to occasionally max out the network interface bandwidth? If not, what are the known issues this could cause? Thank you in advance!