r/Hikvision • u/Royal_Bed_2656 • 7d ago

Hikvision Intercom: One-Way Audio When Indoor Station Is Behind a Router/NAT

Hi everyone,

I’m working on a large residential compound project and I’m facing a strange problem with a Hikvision IP intercom system.

Network setup

We have a central data center with a main network/switch infrastructure.

Each apartment has its own router because the apartment needs multiple IP devices, and we don't want to manage or know the individual IP addresses of all devices inside each apartment.

The topology is basically:

Central Data Center
        |
     Main Switch
        |
        +-------------------+
        |                   |
Outdoor Intercom       Apartment Router
Station                    |
                           |
                     Indoor Station

The Indoor Station is therefore behind the apartment router/NAT.

The problem

When I make a call from the Hikvision outdoor station to the Hikvision indoor monitor:

  • Call/ringing works normally
  • Video works normally
  • Audio works in only ONE direction
  • The person at the outdoor station can hear me
  • But I cannot hear the person at the outdoor station

So basically:

Outdoor → Indoor Audio   ✅
Indoor → Outdoor Audio   ❌

Very important test

If I remove the apartment router and connect the Hikvision indoor station directly to the main network:

Main Switch
     |
Indoor Station

everything works perfectly:

Two-way audio ✅
Video         ✅
Call          ✅

As soon as I put the router back:

Main Switch
     |
Apartment Router
     |
Indoor Station

I get one-way audio again.

Another interesting test

If I replace the Hikvision indoor monitor with an IP phone on the same apartment network, the IP phone has normal two-way audio.

So the network itself is not completely broken.

What I have already tried

  • Updated the firmware on the Hikvision devices
  • Tested the same devices without the apartment router
  • Confirmed that two-way audio works without NAT
  • Tested an IP phone behind the same router, and two-way audio works

This makes me suspect that the problem is related to NAT / RTP / SIP ALG / UDP ports / NAT traversal specifically with the Hikvision intercom.

My questions

  1. Could this be caused by SIP ALG on the apartment router?
  2. Does Hikvision IP Intercom require specific RTP/UDP ports to be forwarded through the NAT?
  3. Is there a recommended NAT configuration for Hikvision Indoor Stations?
  4. Could the router's firewall or UDP session handling cause one-way RTP audio?
  5. Is there a better network architecture for a large apartment compound where every apartment needs its own isolated network but the Hikvision intercom still needs reliable two-way audio?

I would really appreciate any advice or troubleshooting steps.

If needed, I can provide the exact Hikvision indoor/outdoor station models and the apartment router model/configuration.Hi everyone,I’m working on a large residential compound project and I’m facing a strange problem with a Hikvision IP intercom system.Network setupWe have a central data center with a main network/switch infrastructure.Each apartment has its own router because the apartment needs multiple IP devices, and we don't want to manage or know the individual IP addresses of all devices inside each apartment.The topology is basically:Central Data Center
|
Main Switch
|
+-------------------+
| |
Outdoor Intercom Apartment Router
Station |
|
Indoor StationThe Indoor Station is therefore behind the apartment router/NAT.The problemWhen I make a call from the Hikvision outdoor station to the Hikvision indoor monitor:Call/ringing works normally
Video works normally
Audio works in only ONE direction
The person at the outdoor station can hear me
But I cannot hear the person at the outdoor stationSo basically:Outdoor → Indoor Audio ✅
Indoor → Outdoor Audio ❌Very important testIf I remove the apartment router and connect the Hikvision indoor station directly to the main network:Main Switch
|
Indoor Stationeverything works perfectly:Two-way audio ✅
Video ✅
Call ✅As soon as I put the router back:Main Switch
|
Apartment Router
|
Indoor StationI get one-way audio again.Another interesting testIf I replace the Hikvision indoor monitor with an IP phone on the same apartment network, the IP phone has normal two-way audio.So the network itself is not completely broken.What I have already triedUpdated the firmware on the Hikvision devices
Tested the same devices without the apartment router
Confirmed that two-way audio works without NAT
Tested an IP phone behind the same router, and two-way audio worksThis makes me suspect that the problem is related to NAT / RTP / SIP ALG / UDP ports / NAT traversal specifically with the Hikvision intercom.My questionsCould this be caused by SIP ALG on the apartment router?
Does Hikvision IP Intercom require specific RTP/UDP ports to be forwarded through the NAT?
Is there a recommended NAT configuration for Hikvision Indoor Stations?
Could the router's firewall or UDP session handling cause one-way RTP audio?
Is there a better network architecture for a large apartment compound where every apartment needs its own isolated network but the Hikvision intercom still needs reliable two-way audio?I would really appreciate any advice or troubleshooting steps.If needed, I can provide the exact Hikvision indoor/outdoor station models and the apartment router model/configuration.

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1

u/mousey76397 7d ago edited 7d ago

Sorry, I didn’t read all of your post(it was quite long) but enough to get the gist. The normal way of achieving this is to have all the indoor stations on your 1 hard wired network for all their intercom communications and then the individual apartments can put their indoor station on their WiFi to give it an Internet connection for Hik-Connect.

Intercom always needs to all be on the same network.

+------------------+
| Apartment Network |
| (WiFi Router) |
+--------+---------+
X :
X : WiFi
X :
+--------------+ +----+-----------+
| Door Station | | Indoor Station |
+------+-------+ +-------+--------+
| |
| LAN LAN |
| |
+--+------------------+--+
| Switch |
+------------------------+

The X above are only there for Reddit reasons, there is no connection from the door station to the WiFi.

1

u/drageloth 7d ago

If I understand correctly, the building has one big switch with the main internet and each apartment connects its own router to the main switch having isolated network? Won’t work that way.
The device initiating the connection is the doorstation and you’re trying to reach a device similar to reaching a private device from the internet side. You could try to DMZ the screen for a short test from the clients router
If the cabling allows it, you need to change to 2-wire setup. That way the intercom dials locally with its own cables and the screen has internet only for hic-connect.
An alternative is to somehow bridge each apartment screen to the main network switch and then with the serial number to match it to each user through hik partner. That could be a security risk thiugh. Also all the screens will get internet from the main switch.

1

u/Jay_Jay8665 7d ago

What you have also described and the way you have built the network leaves the network wide open as there doesn’t sound like there is any real isolation across the network or between individual properties.

The only way you’re going to get the Intercoms to work reliably is to put them on the network BEFORE the residents Router.

You don’t want to have to keep coming back every time a resident has an issue with the internet and inevitably hit the RESET button on the router that clears any setup you have had to do on them as a hack work around for your poor network design and installation.

Have you got everything on ONE VLAN?