[Samba] Trust relationship

[Julien Addams]

Hello. First of all, excuse my English, I am French.
I would like to create a trust relationship between my two DC Samba4
sc.local and rt.local.
I was surprised to find no documentation on trust relationships.
Using the help, I used the command:

/usr/local/samba/bin/samba-tool domain trust create sc.local
--type=external --direction=both --create-location=both -U
Administrator at sc.local%password

But it answers me:

LocalDomain Netbios[RT] DNS[rt.local]
SID[S-1-5-21-868514845-2905818245-770643559]
RemoteDC Netbios[PDC] DNS[pdc.sc.local]
ServerType[PDC,GC,LDAP,DS,KDC,TIMESERV,CLOSEST,WRITABLE,GOOD_TIMESERV,FULL_SECRET_DOMAIN_6]
RemoteDomain Netbios[SC] DNS[sc.local]
SID[S-1-5-21-1385687273-894974810-3564316924]
smb_signing_good: BAD SIG: seq 1
ERROR: REMOTE_DC[pdc.sc.local]: failed to connect netlogon server -
ERROR(0xC0000022) - Access denied

What is this netlogon server?