In this article we will discuss how can we verify if NAT is working for a specific host.
In the below example customer may raise queries for NAT if working or not and below is an example of the NAT design.
Complete path : Laptop A: 10.10.20.20 ---> (NAT 68.XX.XXX.XXX- ISP)----> 24.XX.XX.XXX (NAT Juniper device)---> 10.10.10.10 Laptop B.
Laptop_B trying to reach out to Laptop_A and Laptop_B is connected to Juniper router configured for NAT or CGNAT services.
Notice the NAT is happening twice at ISP and Juniper Device, customer may reach out having issue with connectivity any for application like MS Team or any other application to verify if NAT is working or not.
Verify using below command and check if packets and bytes counters, if these counters are 0 means no packets are coming in the NAT direction.
Example :
Below output confirms that no packets are received from 10.10.20.20 to 24.XX.XX.XXX and also from ISP 68.XX.XXX.XXX to 24.XX.XX.XXX Juniper device.
show services sessions source-prefix 10.10.10.10 (Laptop_B)
Session ID: 219044366559, Service-set: NAT_44, Policy name: TEST/1015823, Timeout: 58, Session State: Valid
Member name: mams-8/0/0
In: 10.10.10.10/50019 --> 10.10.20.20/50008;udp, Conn Tag: 0x0, If: ams0.1, Pkts: 10, Bytes: 1488,
Out: 10.10.20.20/50008 --> 24.XX.XX.XX/64199;udp, Conn Tag: 0x0, If: ams0.2, Pkts: 0, Bytes: 0,
Session ID: 154637578557, Service-set: NAT44, Policy name: TEST/1015823, Timeout: 60, Session State: Valid
In: 10.10.10.10/50030 --> 68.148.206.170/50030;udp, Conn Tag: 0x0, If: ams0.1, Pkts: 2, Bytes: 280,
Out: 68.XX.XX.XX/50030 --> 24.XX.XX.XX/64222;udp, Conn Tag: 0x0, If: ams0.2, Pkts: 0, Bytes: 0,