Cannot ping DAG IP

I have an Exchange DAG "DAG1" containing three MB servers in 'Site A'. Now i want to
extend the DAG to another site 'Site B' containing one MB server.IP addresses configured
on MAPI network on Mailbox servers are as under

MB1 (Site A) : 10.1.1.1
MB2 (Site A) : 10.1.1.2
MB3 (Site A) : 10.1.1.3

DAG IP is 10.1.1.4

IP address configured on MB in Site B is

MB4 (Site B) : 172.16.22.1.

Since I wanted to add this server in 'DAG1', I added an IP '172.16.22.2' in 'DAG1'.

Now, when ping this ip '172.16.22.2' from 'Site A', it gives 'Request timed out' and
when i ping it from 'Site B', it gives 'Destination Host unreachable'.

I can ping "MB4 (Site B) : 172.16.22.1." from both sites. According to network team all
communication is allowed.

If I add the 'MB4' server to 'DAG1', it cannot retrieve network information, giving error

"A server-side administrative operation has failed. 'GetDagnetworkConfig' failed on the
server'

Can someone help?

Regards

Usman Siddiqui