Why when change frequency USRP x300, frequency change is not change real time???

[sp h]

I record a signal from USRP when I change the frequency USRP from below 80 MHz to 89 MHZ, USRP does not change frequency instantaneously......

USRP frequency change is alike step change and 2 seconds is time to lock completely on 89 MHZ.....

when I ping to address USRP 192.168.10.2 it takes a long .5 ms......But when I changed the frequency of USRP x300 with GUI Gnuradio I see this response. I too test this case in CPP....but...problem yet there is.....

This response screenshot is recorded with another SDR hardware...........

Thanks in advance