Understanding the Output from Diagnostic Commands
171
To emphasize, the switching type depends on two factors: which encap-
sulation is configured on the interface and whether a cache entry exists for
the configured method. Look at Figure 4.6 to see a flow chart that describes
the process for each packet entering a router.
F I G U R E 4 . 6
Switching method and packet flow
Let's work through the flow chart in Figure 4.6. You can see that the
incoming packet is immediately copied to the interface processor buffer. If
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
Interface
buffer
Is this a VIP card
(Y/N)
Copy packet
across the Cx/CyBus
Entered into the
SP/SSP buffer
Check distributed
cache
Check silicone
cache (Y/N)
Entry exists
(Y/N)
Check autonomous
cache (Y/N)
Check optimum
cache (Y/N)
Copy header, send
to the RP
Encapsulate,
copy packet over
Cx/CyBus and send
to the outgoing
interface
Check fast
cache (Y/N)
Copy entire
packet
Process switch
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