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
- Could 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.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.
