Hi Draytek Forum,

I have a Vigor 2920 that is acting as a GW device for a LAN. In the LAN I have a Layer 2 Switch, a IP PBX and a NAS box.

The 2920 has a /26 - 255.255.255.192 - 62 usable public IPs allocated to it and I have 5 of these IPs setup as WAN1 IP aliases at present. (This is just a test scenario so no complaints about the decadent use of IPs!)

From my remote management network I have Solarwinds Network Monitor running and I want to speak to all of the devices using SNMP - Draytek, Switch, PBX and NAS box - all devices support SNMP v2.

If I have the SNMP server disabled on the Draytek that I can use my 5 Public IPs and use NAT to forward the UDP Port 161 requests to the internal devices, almost 121 to NAT. Public IP Alias:Port 161 --> Internal IP:Port 161 which works fine.
(I say it works fine but I did have to overcome an issue and assign a /24 subnet to my public IP rather than the correct /26? to get this to work for several IP aliases..?)

However when I enable the SNMP server on the Draytek then it responds to all of the SNMP requests on all IPs instead of forwarding the requests to the internal devices. Remember I am making requests on different public IPs for each different internal device.

I have tried Port Forwarding, Open Ports and Address mapping and have made the IP aliases part of the NAT Group and not part of the NAT Group to the same result.

Under management options you can change the port for HTTP/SSH/Telnet etc. But no option for SNMP. This would cause me an issue anyway as the version of Solarwinds that I have can only speak on port 161 UDP so I can even make the public request on a different port say 163 and then trigger this to the internal 161 port.

Therefore is there a way of having the SNMP enabled on the Draytek but only have it respond to SNMP requests on the WAN1 IP and not respond to the WAN IP aliases? Either that or if there is port forwarding setup it looks to these rules first before the requests gets forwarded to the Draytek SNMP server?

Kind regards,

James

To simplify my request/issue, I am trying to achieve this;

IP 1.1.1.1 Port 161 --> Draytek SNMP Server
IP 1.1.1.2 Port 161 --> NAT --> 192.168.1.2 Port 161
IP 1.1.1.3 Port 161 --> NAT --> 192.168.1.3 Port 161
IP 1.1.1.4 Port 161 --> NAT --> 192.168.1.4 Port 161

So I want the main WAN IP to speak to the Draytek SNMP service/Server, but on all IP aliases I want it to port forward to the internal devices.

It would seem that with the SNMP Server enabled on the Draytek it will answer all SNMP requests and will not take notice of the port forwarding rules.

I have a Cisco 811 and I am able to get this to work fine on this device