Final answer:
Configuring both sides of a port channel with 'on' mode creates a static EtherChannel that increases bandwidth by aggregating multiple links. It does not use negotiation protocols, which can risk misconfiguration and connectivity issues.
Step-by-step explanation:
When configuring a port channel with both sides set to 'on' mode, you are manually enabling EtherChannel without any negotiation protocols such as PAgP or LACP. This is sometimes referred to as a static EtherChannel. This setup will successfully establish a port channel if both ends of the link have their interfaces configured with the 'on' mode. By doing so, the link will act as a single aggregated connection, effectively increasing the bandwidth by combining the capacities of the individual links that form the port channel.
However, it's important to be cautious with this configuration; if one side is mistakenly set to a different mode or not configured correctly, the link won't form a port channel and might result in inconsistencies or connectivity issues. Using a negotiation protocol minimizes the risk of these configurations errors, as it ensures that both sides agree on forming the port channel before it gets established.