Enables IPv4 forwarding on a physical or virtual Ethernet interface that is configured for IPv6 only.
By default, IPv4 forwarding is disabled on physical and virtual Ethernet interfaces.
Interface subtype configuration mode
When IPv4 forwarding is enabled on an IPv6 interface, IPv4 packets are accepted and forwarded over the interface.
IPv4 forwarding configuration is only allowed on Layer-3 interfaces that have an IPv6 address or IPv6 address link-local configuration. IPv4 forwarding configuration is not allowed on interfaces with an unnumbered or IPv4-address configuration. Similarly, when IPv4 forwarding is configured on an interface, you cannot configure the interface as an unnumbered interface or with an IPv4 address.
When IPv4 forwarding is configured on an interface, you cannot delete the last IPv6 address configuration on that interface.
The no form of the command disables IPv4 forwarding on a physical or virtual Ethernet interface.
The following example shows how to enable IPv4 forwarding on physical Ethernet interface 0/5.
device# configure terminal device(config)# interface ethernet 0/5 device(conf-if-eth-0/5)# ip forward
The following example shows how to enable IPv4 forwarding on virtual Ethernet interface 10.
device# configure terminal device(config)# interface ve 10 device(conf-if-ve-10)# ip forward