in the link to the docs you mentioned, under the section “Communication Channels” it says:
[QUOTE]At least two TCP/IP communication media per cluster node. The network equipment must support the communication means you want to use for cluster communication: multicast or unicast. The communication media should support a data rate of 100 Mbit/s or higher. For a supported cluster setup two or more redundant communication paths are required. This can be done via:
Network Device Bonding (to be preferred).
A second communication channel in Corosync.[/QUOTE]
So I guess you’re not forced to, but it’s recommended to bond the interfaces.