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Based on SDN, data plane's main function is to store and forward packets based on controller's instructions (in the form of flow rules). While I was reading OpenFlow Specification v5.1, I came across to Set-field Action set which can modify the packet header. My question is: Can OpenFlow-based Switch go further than just forwarding to modify the packet header such as changing the IP address?

Thank you.

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Yes.

To be more precise, the openflow protocol defines the set-field action, but it depends on the switch implementation whether or not it supports this, and which fields can be modified if it does.

E.g. this doc mentions that the openflow agent on Cisco NXOS switches support (among others) following actions:

  • Rewrite source MAC address (SMAC) Supported for the Ethertype values 0x0800 or 0x86DD (IP) only
  • Rewrite destination MAC address (DMAC) Supported for the Ethertype values 0x0800 or 0x86DD (IP) only
  • Rewrite VLAN ID Supported for the Ethertype values 0x0800 or 0x86DD (IP) only
  • Strip VLAN (Supported for the Ethertype values 0x0800 or 0x86DD (IP) only)

Note Rewrite DMAC and Rewrite SMAC actions must be specified together.

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