A physical port has three associated buffer pools. Which of the following buffer pool combinations is associated to a physical port?

Question

Options

• AAccess ingress, access egress, network egress
• BAccess ingress, network ingress, network egress
• CPort ingress, port egress, shared bi-directional
• DPort ingress, port egress, network egress
• EPort ingress, network ingress, network egress

• A
  85% (17)
• B
  10% (2)
• E
  5% (1)

Explanation

Option A is correct because, in Cisco's QoS buffer pool architecture, each physical port is associated with exactly three pools: access ingress (buffering traffic arriving from the edge/user side), access egress (buffering traffic departing toward the edge/user side), and network egress (buffering traffic departing toward the network/core side). The network ingress direction is handled at a higher shared level rather than being tied to an individual physical port, which is why option B is wrong. Options C, D, and E all introduce "port ingress" and/or "port egress" terminology, which is not the correct naming convention in this buffer pool model - these are not valid pool designations in the access/network ingress-egress framework. A helpful memory tip: think "A-A-N Egress" - two Access pools (one in, one out) plus one Network egress pool per port; the only direction missing is network ingress, because that is shared upstream, not owned by the individual port.

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