E1 PRI Clock Sourcing Question

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May 27th, 2008
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Hello,


I'm configuring the following scheme: CUCM <mgcp> 2821 <e1-pri> 2821 <fxs> analog phone.


Have a question about how to avoid different violations and errors (they are accumulated for now) on E1 controllers.


1. The first 2821 router I've configured the following way (among others):


- "External clock" in the endpoint configuration in CUCM Administration

- "network-clock-participate wic 1"

- "show controller e1" tells that 'Clock Source is Line'

- ISDN L2 is up, D-channel (CUCM controlled) is up


2. The second 2821 router I've configured the following way (among others):


- "network-clock-participate wic 1"

- "show controller e1" tells that 'Clock Source is Line'

- ISDN L2 is up, D-channel is up


As I see, the clock source can be only one.

I have no routers except these two.


So how can it be possible to regulate the clock between them ?

Correct Answer by paolo bevilacqua about 8 years 11 months ago

Hi, on both routers are "network-clock-select 1 E1 1/0".


Slips will cease and you will be fine.


Hope this helps, please rate post if it does!

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Correct Answer
paolo bevilacqua Tue, 05/27/2008 - 04:16
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Hi, on both routers are "network-clock-select 1 E1 1/0".


Slips will cease and you will be fine.


Hope this helps, please rate post if it does!

Tobivan_Helden_2 Tue, 05/27/2008 - 05:10
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Paolo,


1.


As always you've driven the centre. That's great !

After reconfiguring the message occurs


"%MARS_NETCLK-3-CLK_TRANS: Network clock source transitioned from priority 10 to priority 1"


And controllers are fine now :)


2.


Could you please also explain the mechanism of the fix ?

As I've found in documentation, 'network-clock-select' just

prioritizes clock sources if there are more than one.


<< CITED BEGIN


{ network-clock-select


When an active clock source fails, the system chooses the next lower priority clock source specified by this command. When a higher-priority clock becomes available, the system automatically reselects the higher-priority clock source.


}


<< CITED END


Thus it doesn't absolutelty clear for me what has been happened :)

Both routers have had the same source, and the problem has been solved only after I had prioritized theirs sources. Hm...

paolo bevilacqua Tue, 05/27/2008 - 05:27
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Hi, what the manual doesn't say, is that the VWIC card MUST have the selected "network-clock" to be same circuit that is connected to, else slips will happen.


Slips are not a serious problem for data and voice, but cause fax and modem to fail.


Thanks for the appreciation and good luck!


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