Cisco CCNA CCNP Certification Tutorial Frame Relay End-To-End Keepalives
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Cisco CCNA/CCNP Certification Tutorial: Frame Relay End-to-End Keepalives
Overview
While many are familiar with Frame Relay's Local Management Interface (LMI) as a keepalive, few realize that Frame Relay also supports end-to-end keepalives. These are crucial for ensuring seamless communication between endpoints. Let’s delve into these details, essential for your Cisco exams, with insights from Chris Bryant, CCIE
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Understanding Frame Relay Keepalives
Frame Relay's LMI acts as a local keepalive, ensuring connectivity between the Data Terminal Equipment (DTE) and the nearest Data Circuit-terminating Equipment (DCE). If three consecutive LMIs are missed, the line protocol falls. However, LMI only monitors local connectivity and doesn’t account for issues at the remote side of the virtual circuit.
To address this, Cisco uses Frame Relay End-to-End Keepalives (FREEK) to confirm the proper functioning of communications across endpoints.
How FREEK Works
FREEK requires two separate keepalive processes for each Permanent Virtual Circuit (PVC). Note that the path for data from R1 to R2 through the Frame Relay cloud might differ on the return journey. Thus, two processes are necessary:
- Send Side: This process sends keepalive requests and waits for a response within a set time (10 seconds by default). Failure to receive a response prompts an error event. Accumulating two such events within three consecutive tries (event window) marks the VC’s keepalive status as down.
- Receive Side: This responds to keepalive requests from the other end.
FREEK Operational Modes
Cisco provides four modes for FREEK:
1. Bidirectional Mode: Enables both sending and receiving processes on the router. The router can initiate requests and respond to those from other routers.
2. Request Mode: Only the send process is operational. The router sends requests but does not respond to any.
3. Reply Mode: Only the receive process functions. The router responds to requests but doesn’t initiate any.
4. Passive Reply Mode: The router responds to requests without initiating them, setting timers, or tracking events.
FREEK Defaults
- A Virtual Circuit (VC) is flagged as down if two send or receive errors occur within the event window.
- The event window size is three.
- The default wait time for a response after sending a keepalive request is 10 seconds.
Conclusion
Mastering Frame Relay end-to-end keepalives is one of the many skills required for the CCNP exams. It's a topic that could appear on the CCIE exam as well. Understanding these details will significantly enhance your Cisco certification preparedness. Keep studying, and you’re on your way to success!
You can find the original non-AI version of this article here: Cisco CCNA CCNP Certification Tutorial Frame Relay End-To-End Keepalives.
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