Symptom
C9200/9200L: Link up detection delay after bootup
Conditions
- Linkup may take 2-3 minutes after bootup when shutdown is configured on at least one physical port.
- Linkup may take 20-40 seconds after bootup when shutdown is not configured on any physical ports.
Workaround
set "SKIP_POST=1" in rommon prompt.
switch: SKIP_POST=1
Further Problem Description
The main issue which is 180sec delay is no more seen with latest 1612_throttle, In past we have fixed this issue.
Though still we are observing 20-24 sec delay, we are working to optimize this delay too.
The root cause of this problem is that,
In 9200 platform we disable the link polling till POST is completed, IOS detects the link up once polling is enabled.
Since we initialize the phy and asic little early before even POST completes, Peer sees the link up first and IOS detects it bit later once POST completes.
Which results in this delay, There is no functionality impact.
This behaviour will be observed only when the switch is booting up, once switch is up and running there would be no delay observed in native link up.
The workaround of this issue is SKIP_POST=1. >>> if we skip the POST, No native delay will be observed even during bootup.
Cause for the issue fixed in past resulting in 180 sec delay : [if shut config is present for any port the mac loopback test was failing for first trial which adds 3-4 sec delay per port during POST, hence for 48port board, it takes 2-3 minutes time for POST to complete, hence IOS detects the link up bit later then native].
