Transparently Intercept and Redirect DNS Traffic to an Internal DNS

Marv21

@ibbetsion
The NAT Rule is only valid for the .7. net?

gniting

@Marv21 the redirect NAT rule is set up for the .7. net.
In the image below, SYNAPSE_LAN = .7. net.

Marv21

@ibbetsion
dns_ok is 192.168.8.2 then - right?

Marv21

@ibbetsion

Where are you running this Dig command from?
A client from the 7 or the 8 Net?

gniting

@Marv21 Sorry for omitting that, dns_ok is an alias that I use for those hosts that are allowed to make queries to external DNS servers. Any local host not in this alias/group should be re-routed to the local DNS server at 192.168.8.2

gniting

@Marv21 the dig command is running from a host on the 7 Net.

johnpoz

@ibbetsion said in Transparently Intercept and Redirect DNS Traffic to an Internal DNS:

; reply from unexpected source: 192.168.8.2#53, expected 8.8.8.8#53

No shit what do you think was going to happen... This is why you put your NS your going to redirect to on a different vlan.. Or you have to forward it to loopback.. So pfsense does the query, and then sends the answer..

gniting

@johnpoz the NS is on a different subnet...

Marv21

@ibbetsion

could you try this just 4 fun?
Thats mine. So everything will be redirectet from LAN to the SYNAPSELAN (any - directed to to that net or not)

gniting

@Marv21 said in Transparently Intercept and Redirect DNS Traffic to an Internal DNS:

@ibbetsion

could you try this just 4 fun?
Thats mine. So everything will be redirectet from LAN to the SYNAPSELAN (any - directed to to that net or not)

That caused all DNS resolution to stop working. I think the issue is somewhere else. I am also now finding out that I cannot ping (or ssh) from the 8 Net to anywhere on the 7 Net or anywhere else. But I can go from 7->8 Net. Need to solve that first :)

Marv21

@ibbetsion
Have you a allow Rule on the 8 net?
YOu need to allow traffic to 7.

gniting

@Marv21 said in Transparently Intercept and Redirect DNS Traffic to an Internal DNS:

@ibbetsion
Have you a allow Rule on the 8 net?
YOu need to allow traffic to 7.

Yes, there is an allow rule on 8.

johnpoz

@ibbetsion said in Transparently Intercept and Redirect DNS Traffic to an Internal DNS:

the NS is on a different subnet...

You can not run multiple layer 3 on the same layer 2 and call it a different network..

For what your seeing to happen, the NS you redirected to had direct access to answer the client..

. I am also now finding out that I cannot ping (or ssh) from the 8 Net to anywhere on the 7 Net or anywhere else.

Seems you have bigger issues in your network than just trying to redirect dns..

gniting

@johnpoz I was able to resolve the other issues. Everything is on track except for the unexpected source issue.

A bit more on the network setup.

ISP modem connected to pfsense on WAN port
pfsense's LAN1 port connected to an unmanaged switch which in turn has all other local devices on it
pfsense's OPT1 port connected directly to host running DNS/pihole

LAN1=192.168.7.x network
OPT1=192.168.8.x network

johnpoz

Then what your seeing makes zero sense...

So I can for sure duplicate your problem when the NS is on the same network..

root@ntp:/home/pi# dig @8.8.8.8 www.google.com
;; reply from unexpected source: 192.168.3.10#53, expected 8.8.8.8#53
;; reply from unexpected source: 192.168.3.10#53, expected 8.8.8.8#53

But if I put it on a different subnet works fine, or if forward to loopback, or if setup nat reflect auto outbound nat rules so it

You can see from this sniff, pfsense saw traffic to 8.8.8.8, sent it on from its own interface 3.253 to 3.10, got answer and then sent answer back to 3.32 looking like it came from 8.8.8.8

But yes if client thinks it sending to A, and gets back answer from B - its going to complain.

gniting

@johnpoz makes zero sense to me too, hence the continued head-scratching

I do have the option enabled to Enable automatic outbound NAT for Reflection. On your network, you have the NAT redirect rule and that's it?

Marv21

@ibbetsion
Both are /24 ?

gniting

Yes

Marv21

@ibbetsion
Hmm.
What you could try (if you have not done any own modifications in the filesystem) - Backup everything, reinstall Pfsense und roll back the Backup.
I had it once a while (4years or greater) that i had done this and suddenly everything was ok.

Is this a Virtualized Maschine or something?

Could you post all NAT Rules, Outbond Page, Lan Rules and DNSNet rules here as Screenshots?

Do you have any Floating Rules?

johnpoz

@Marv21 said in Transparently Intercept and Redirect DNS Traffic to an Internal DNS:

s this a Virtualized Maschine or something?

That is a great question...

Why don't you just sniff and see exactly what is happening..

I don't intercept traffic on the same interface and send back in, but yes that outbound nat automatic should do make it look like i comes from the pfsense interface in that network when you do it that way..

If pfsense redirects traffic and doesn't nat it or is not the gateway for the return.. Then yes your client is going to scream at you you - wtf is this I sent to A, why is B sending me a response.