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Packet Processing with Static Routes

  1. The packet arrives on the interface of R1.
  2. R1 does not have a specific route to the destination network; therefore, R1 uses the default static route.
  3. R1 encapsulates the packet in a new frame. Because the link to R2 is a point-to-point link, R1 adds an “all 1s” address for the Layer 2 destination address.
  4. The frame is forwarded out of the appropriate interface. The packet arrives on the interface on R2.
  5. R2 de-encapsulates the frame and looks for a route to the destination. R2 has a static route to the destination network out of one of its interfaces.
  6. R2 encapsulates the packet in a new frame. Because the link to R3 is a point-to-point link, R2 adds an “all 1s” address for the Layer 2 destination address.
  7. The frame is forwarded out of the appropriate interface. The packet arrives on the interface on R3.
  8. R3 de-encapsulates the frame and looks for a route to the destination. R3 has a connected route to the destination network out of one of its interfaces.
  9. R3 looks up the ARP table entry for the destination network to find the Layer 2 MAC address for PC3. If no entry exists, R3 sends an ARP request out of one of its interfaces, and PC3 responds with an ARP reply, which includes the PC3 MAC address.
  10. R3 encapsulates the packet in a new frame with the MAC address of the appropriate interface as the source Layer 2 address and the MAC address of PC3 as the destination MAC address.
  11. The frame is forwarded out of the appropriate interface. The packet arrives on the network interface card (NIC) interface of PC3.

Troubleshoot IPv4 Static and Default Route Configuration

Networks are frequently subject to events that can cause their status to change. An interface can fail, or a service provider drops a connection. Links can become oversaturated, or an administrator may enter a wrong configuration. Common IOS troubleshooting commands include the following:

  • ping
  • traceroute
  • show ip route
  • show ip interface brief
  • show cdp neighbors detail

16.3.4 Module Quiz – Troubleshoot Static and Default Routes