topic Re: Additional NAT rule 0 in Firewall & Security Management

Additional NAT rule 0

AaronCP — Tue, 27 Jul 2021 07:35:02 GMT

Good morning,

I have a manual static NAT rule configured in our rulebase:

Original Source: x.x.x.x - Original Destination: y.y.y.y - Original Service: any - Translate Source: Original - Translate Destination: z.z.z.z - Translate Service: original

The NAT rule itself works fine. In the logs, I can see the traffic is hitting the correct NAT rule (NAT rule 10, for example), but I can also see "NAT Additional Rule Number 0" in the logs. Initial research suggests that this is related to bi-directional NAT (which is enabled in Global Properties), but I thought this was only applied to automatic rules? Not manual? This is happening on the majority of our NAT rules, most of which are manual.

R80.40, take 118.

Can someone help clarify this, please?

Thanks.

Re: Additional NAT rule 0

Timothy_Hall — Tue, 27 Jul 2021 17:31:48 GMT

I'm a bit hazy on this but NAT rule 0 applies in the following situations I can think of:

1) NAT "Hide Internal networks behind gateway's external IP" is set on the gateway/cluster object (not default setting)

2) Certain traffic to and from cluster member themselves, including control traffic

3) Traffic matching the implied Firewall policy rules (Actions...Display Implied Rules) from Security Policies tab in SmartConsole

4) Possibly lack of inspection/handling due to Wire Mode

Re: Additional NAT rule 0

net-harry — Thu, 23 Sep 2021 12:57:47 GMT

Hi,

I have a related question regarding NAT Additional Rule Number.

We have a NAT rule that translated various internal subnets to a hide-NAT address.

The logs that hits this NAT rule correctly shows the NAT rule number (NAT rule #8 in our case), but it also shows a "NAT Additional Rule Number". For most entries it is 1, but for some entries it is 0.

Could someone explain what this means and the reason this is happening?

Please note that:

NAT rule #1 does not at all match the traffic for the log entries with this behavior
We do not have "Hide Internal networks behind gateway's external IP" enabled on the gateways
We do not have "Allow bi-directional NAT" enabled in the global properties
This is traffic from inside subnets, not addresses on the firewalls themselves

We are running R80.40 on the MDS servers and R80.20 on the security gateways.

Thanks for your help!

Harry

Re: Additional NAT rule 0

Timothy_Hall — Fri, 24 Sep 2021 12:31:42 GMT

Normally the NAT additional rule number should be blank unless two automatic rules were matched (one for source and one for destination), but according to sk144192:

When matching 2 automatic rules, second rule match will be shown otherwise NAT Additional Rule field will be 0.

So that explains the NAT additional rule being 0 when matching only one automatic rule. If a manual NAT rule is matched, only that one rule can be matched and the NAT additional rule should always be blank (or maybe 0). Not sure why the field would show 1, perhaps it is trying to indicate that only one NAT rule (a manual one) is matched? There were some changes to NAT made in R80.40 involving GNAT & exhaustion pools and such, perhaps this behavior change in the logs is related to that?