Azure networking port 4500 outbound

Jakezxz1 40 Reputation points

Good evening,

I am looking to setup a IPsec tunnel between my lab router and my VM which is running Sonicwall NSv270.

I have configured this to be a policy based tunnel.

The configuration for both the SA's and the proposals is exact and matching at both sides.

My lab router is a cellular router - I am using NAT-T to encaspulate IP protocol 50/51 into UDP port 4500.

Using a Pcap on the VM (Sonicwall NSv) I can see traffic entering/leaving the appliance on ports 500 and 4500.

Using a Pcap on the router, I cannot see return traffic from my VM on port 4500.

I know this is not my cellular provider because I have devices in my network which are sending/receiving packets on port 4500.

I know it's not the sonicwall because I can see packets leaving on 4500.

I know it's not my NSG because It has the standard Any/Any rule outbound.

I know it's not the cradlepoint either because as mentioned, other devices in my network are sending/receiving packets on this port.

Something in the middle is dropping the packets and I cannot understand where.

Is this an Azure issue? Is anyone able to advise some troubleshooting steps that I haven't already covered?

Thank you in advanced.

Azure Virtual Network
Azure Virtual Network
An Azure networking service that is used to provision private networks and optionally to connect to on-premises datacenters.
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  1. risolis 8,241 Reputation points

    Hello @Jakezxz1

    Thank you for posting this concern on this community.

    I just wanted to double check if the following details were reviewed as shown down below:

    -Did you check for any asymmetric routing path issue?

    -How is your routing set up on your NVA (Network virtual appliance)?

    -Do you have just one internet provider or dual internet provider?

    -How did you set up your NAT on your NVA?

    -Did you configure any VM behind the firewall and check internet connectivity?

    Looking forward to hearing from you


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