VC12 trail cannot be created

Hello friend！

Before creating a VC12 service, you need to create a VC4 server trail, as shown in the following figure. 

Thank you！

Hi user hope below can help:

The VC12 or VC3 service being created traverses NEs whose main control board versions are 4.XX.XX.XX, but no protection subnet has been created for links on these NEs.

1. Create protection subnets on NEs whose main control board versions are 4.XX.XX.XX.

2. Create a VC12 or VC3 trail again. For details, see Chapter SDH and Radio Trails Management>Creating SDH Trails in the OG for MSTP and Radio Services Management.

https://support.huawei.com/huaweiconnect/carrier/en/thread-43573.html

hi
from your picture you attached , it seems that u haven't created the fiber link between stations yet.
you should start with:-
1- creating fiber between stations according to the real fiber connection .
2- in some U2000 versions u must create protection on the fiber before be able to create service and if u donot have a protection on fiber , u should then create (no protection Chain or no protection ring ) on this fiber.
3- then start creating service :- 1st create VC4 server trail , 2nd creat VC12 trail .

best regards

@Malink3000
Thank you very much for your answer!
I would like to ask you again: Why do I need to create a VC4 server trail before creating VC12 and VC3 services? However, I do not need to create a VC4 server trail before creating a VC4 service.

HI,
To create service using Trail u must create VC4 server trail first , because it acts as a tunnel from point to point ,
that makes :-
1- definite paths for the services , for example if u make VC4 server trail from NE-1 to NE3 passing through NE-2 then the services attended to go from NE1 to NE3 will go on this VC4 server Trail passing directly through this definite path .(u can make a VC4 server trail passing through long series of NEs making creating services by 1 click possible)
2- The NE will have limited number of possible tunnels to create low service rates on .
3- collects services going from same source to same destination .
4- make it easier for cross connect boards to process services for the NEs in the middle of the path .
5- Makes it easier to build protection scenarios .
6- makes ASON-SDH protection possible , as ASON usually change traffic service according to VC4 server trail .