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Understanding the Output from Diagnostic Commands

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This is just another reason why switching is such a good practice. Why

burden the route processor with every packet if it's not necessary? By using
switching methods, the route processor is free to use valuable CPU time
on more important things than doing route lookups for every packet that
comes into the router.

There are times when a packet must be processed or process-switched,

however. For this reason, the router is engineered so that it can handle the
processing and process switching of numerous packets. A system of buffers
and queues exists on the route processor, switch processor, and inter-
face processor that allows packets to be held, processed, and forwarded with
few packet drops. Different router types have different buffer architecture,
so we'll discuss each type in detail.

Buffers and Queues in the Cisco 7000 Series

For the 7000 series routers, the system buffers reside on the RP, with the
memory being allocated from the system memory. The buffers on the RP are
used to store packets that are waiting to be processed by the CPU.

The buffers come configured with default settings. They can be modified,

if necessary, but it is usually a good idea to have a Cisco TAC engineer look
at the memory allocation and suggest the new buffer settings. Following is an
example of the buffer settings:

Buffer elements:

499 in free list (500 max allowed)

32642751 hits, 0 misses, 0 created

Public buffer pools:

Small buffers, 104 bytes (total 120, permanent 120):

110 in free list (20 min, 250 max allowed)

15486216 hits, 322 misses, 364 trims, 364 created

26 failures (0 no memory)

Middle buffers, 600 bytes (total 90, permanent 90):

87 in free list (10 min, 200 max allowed)

3984956 hits, 113 misses, 105 trims, 105 created

36 failures (0 no memory)

Big buffers, 1524 bytes (total 90, permanent 90):

88 in free list (5 min, 300 max allowed)

471484 hits, 24 misses, 6 trims, 6 created

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