A network administrator is troubleshooting an issue where users are experiencing very slow loading times for certain web pages that contain a significant amount of encrypted traffic (HTTPS). Decryption is enabled on the Palo Alto Networks firewall for outbound traffic. The firewall's data plane CPU utilization is consistently high, and the session table shows a large number of sessions with 'decrypt-mirror' or 'decrypt-forward' flags. What is the MOST likely cause of the slow loading times?
- AThe decryption policy is misconfigured, causing traffic to be re-encrypted multiple times.
- BThe firewall's hardware resources (e.g., decryption card) are insufficient for the volume of decrypted traffic.
- CThe firewall is running out of session capacity due to too many concurrent connections.
- DThe certificate authority (CA) certificate used for decryption is not trusted by the client browsers.
Show answer & explanationAnswer & explanation
Correct answer: B. The firewall's hardware resources (e.g., decryption card) are insufficient for the volume of decrypted traffic.
High data plane CPU utilization and slow performance specifically with decrypted traffic, indicated by 'decrypt-mirror' or 'decrypt-forward' flags (which show successful decryption processing), strongly suggest that the firewall's decryption capabilities (hardware or software) are overwhelmed. Decryption is a resource-intensive process, and insufficient hardware can become a bottleneck.
Why the other options are wrong
- A. A misconfigured decryption policy might cause decryption failures or incorrect handling, but not necessarily high CPU *and* successful decryption flags ('decrypt-mirror'/'decrypt-forward') leading to slow performance.
- C. While session capacity can cause issues, the specific focus on decrypted traffic and high data plane CPU points more directly to decryption resource exhaustion.
- D. If the CA certificate were not trusted, users would receive browser warnings or errors, not necessarily slow loading times due to high firewall CPU.
Decryption Performance Bottleneck
Decryption is a computationally intensive process. If a firewall's hardware resources are insufficient for the volume of encrypted traffic being decrypted, it can lead to high CPU utilization and degraded network performance.
- Decryption consumes significant CPU and memory.
- Hardware acceleration (e.g., FPGA, crypto chips) can improve performance.
- High data plane CPU with successful decryption indicates resource exhaustion.
Memory trick: The firewall is trying to read too many secret messages at once, it's getting tired!