HPE7-A06 · Question #72
Drag and Drop Question Match the AOS-CX switch BGP keepalive and holddown timers to the default. Answer:
The correct answer is 60 seconds; 180 seconds. BGP Keepalive & Hold-Down Timers - Default Values The Answer | Position | Timer | Default | |----------|-------|---------| | 1 | Keepalive | 60 seconds | | 2 | Hold-Down (Hold Time) | 180 seconds | --- Why These Values? 1. Keepalive = 60 seconds BGP peers send keepalive…
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Correct arrangement
- 60 seconds
- 180 seconds
Explanation
BGP Keepalive & Hold-Down Timers - Default Values
The Answer
| Position | Timer | Default |
|---|---|---|
| 1 | Keepalive | 60 seconds |
| 2 | Hold-Down (Hold Time) | 180 seconds |
Why These Values?
1. Keepalive = 60 seconds
BGP peers send keepalive messages periodically to signal "I'm still alive." The RFC 4271 standard (which AOS-CX follows) sets the default at 60 seconds. This is the interval between heartbeats - not a failure threshold.
2. Hold-Down = 180 seconds
The hold-down timer defines how long a router waits without receiving a keepalive (or any BGP message) before declaring the peer dead and tearing down the session. The default is 180 seconds.
The relationship is always: Hold-Down = 3 × Keepalive (60 × 3 = 180). This ratio is mandated by RFC 4271 - the hold time must be at least 3× the keepalive interval to tolerate up to two missed keepalives before declaring failure.
Why the Distractors Are Wrong
| Value | Why it's wrong |
|---|---|
| 15 seconds | Common in fast/aggressive BFD-assisted configs, not default BGP |
| 50 seconds | Not a standard BGP timer value |
| 5 minutes / 10 minutes | Not standard default BGP timers (though some older OSPF defaults use similar values) |
Common Misconceptions
- Confusing keepalive with hold-down: Keepalive is the sending interval; hold-down is the failure detection threshold. They are not the same thing.
- Assuming 3-second keepalive / 9-second hold-time: These are popular tuned values for fast convergence, not defaults.
- Thinking hold-down = 2× keepalive: The standard multiplier is 3×, not 2×.
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