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ISR 4400 to receive clocking from carrier and then to pass it to different ISR 4400 as master

Level 1
Level 1

hi all 


I have a config. where the PSTN ISR 4400 needs to receive clocking from the carrier and then to pass it on on a different controller to another internal ISR 4400. 

so far I think that the PSTN ISR receiving it should be config as clock source line primary while the interface connected to the internal ISR should be configure as clock source internal





controller E1 0/1/0

description PSTN line

framing no-crc4

clock source line primary 

pri-group timeslots 1-31



controller E1 0/1/1

description to provide clocking as master

clock source internal


on Internal ISR 



controller E1 0/1/1

description to receive clocking from pstn E1 0/1/1

clock source line primary



do you think this is a sound config and should work ?


thank you




5 Replies 5

thanks went through the links, there is a bit of contradiction 


one says that we need to configure the interface as protocol-emulate network



controller e1 0/1/1

clock source network


interface Serial 0/1//:15

isdn protocol-emulate network


while the other link mentions 


controller e1 0/1/1

clock source internal ??


also believe these needs to be done on the pstn router ?



When ever I have setup a router to provide clocking I've always set emulate network on the interface that should give the clock to something else. Yes it would be on the PSTN gateway where you configure this on the interface that is facing inwards to the equipment that you'd want to provide clock to.


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ok thank will try that in a bit. 


shall I use clock source internal or network on that particular controller ?


also on the receiving 4400, I think I use clock source line primary to receive it from the pstn gw - correct?

Test one, if it works than all is fine, if not test the other. It's not like the thing will explode or something. Yes on the router you want to receive clock you'd configure that as if you connected it to a PSTN connection. It's not any more fancy than that.


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