We've got SIP trunk between CUCM 6 and CUCM 8
The problem is that particular numbers from particular partitions and CSS from CUCM 6 can not reach phones on CUCM 8. However, some other numbers from CUCM 6 with the same CSS and Partition can dial to CUCM 8. To be more specific, I will give you and example.
Imagine, there is a number 6401 with CCS1 and Partition1. This number is unable to reach CUCM8. But, there is another number, 6402 with CSS1 and Partition1 which can reach CUCM8. Moreover, if I reset 6401, or change partition order in CSS1, 6401 dials to CUCM8 for a period of time, but then stops working again.
If I put 6401 in CSS2 and Partition2, in which other phones can reach CUCM8, 6401 works for a period of time, and then again fails to call to CUCM8
Calls from CUCM8 to 6401 are always succesfull. I tried to recreate CSS1, it did not help.
DNA from 6401 to CUCM8 show "Route this pattern".
I am out of thoughts, will appreciate any help. Thank you in advance.