A network device receives control plane packets and data plane packets
from a network. The network device includes a forwarding component that
forwards the data plane packets in accordance with routing information
maintained by a routing component. The forwarding component directs the
control plane packets to a firewall component that processes the control
plane packets to apply firewall services and detect network attacks.
After processing, the firewall component loops the control plane packets
back to the forwarding components for forwarding to the routing
component. The firewall component may be a security service card.