PBF conflict with "ip strict option" in zoon protection

[Elmokadem]

Hi All

i have a scenario where the traffic works fine if it's forwarded by the routing table (and nat is applied)

when i used pbf, it didn't work, checking global counters i found oacket are dropped and the reason is "strict ip" option in the zone protection profile.

I run debug flow basic and got this message : 

"source ip address in packet does not belong to interface address, packet dropped" 

unchecking this option fixed the issue.

I did little research on this option and found it's releated to malformed packets not spoofing 

we have spoofing check enabled but it's not affecting the operation (tried disabling it but everything is same)

So i see strict is making the spoof check but on the return traffic . Is that normal ?! 

PAN OS 9.0.9-h1

Thanks!

[MP18]

@Elmokadem 

Please see below document.

Also Recommended version for 9.1 is 9.1.4.

Regards

Mahesh

[Elmokadem]

@MP18 

I couldn't see any document below , could you please share it. 

For the PAN OS , customer is still running 9.0 , is this topic related to the upgrade to 9.1 ?

Thanks

[Abdul-Fattah]

Hi,

from the little infos you wrote on your problem i will say, you have a problem with the returning traffic.

just use "enforce symmetric return".

[Elmokadem]

Hi @Abdul-Fattah Thanks for your reply . We tried already, result is same . We had to uncheck "strict ip" .

Why "strict ip" is affected by the routing,! isn't it for malfored packets/reserved IPs ,.. ?

[Abdul-Fattah]

as you can see below Stict Ip check can affect Incoming packets and match the error desc you were seeing

[MP18]

@Elmokadem 

Not related to upgrade it is just suggestion.

Here is link to document

https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClzeCAC

Regards

[Elmokadem]

Hi @MP18 , thanks for your reply. Yes, spoofing is understanable but "IP strict" isn't 

@Abdul-Fattah  thanks for sharing the defination for "IP strict", but as per the defination, this might happen only on the ingress interface, for our case c2s is counting while s2c is zero, until we uncheck "strict ip"!

Thanks again

[Abdul-Fattah]

Thats exactly what should happen.
Glade that it works now.

Good Luck.

[Elmokadem]

@Abdul-Fattah  yeah it already works with disabling "strict IP" so this is my question , why should i disable it ? even with the guide you shared it might only affect ingress interface

[Abdul-Fattah]

ingress interface when traffic enters the Firewall, when client send to firewall that is an ingress interface, when a server send to firewall that is an ingress interface.

Strict IP is a security feature, but in your case "in your Environment"  you can not use it. because after using BPF obviously one these two conditions not filfilled. so you will need to investigate the matter further. and make some changes in your network.

or simply disabling it.

[TravisC · Accepted solution]

The s2c traffic is dropping because of Strict IP is failing due to the source IP address is not routable over the exact ingress interface. The firewall decides if the address is routable by checking the routing table to see if a route exists for the server to use that interface.

Disabling Strict IP Address Check would allow the s2c traffic through the firewall, but it also introduces a security risk for that zone as well.

A better solution would be to add a route for the server address to use that interface. This would allow Strick IP Address Check can stay enabled and the routable check to succeed.

[Elmokadem]

Thanks @TravisC for the explanation , i marked your post as the solution as you explained it very well. 

I am now wondering why "spoof IP" and "strict IP" are doing the same function?!

[Abdul-Fattah]

@Elmokadem 
Can you share why you would need BPF if you can simply add a route to the server in VR?

Spoof IP: if source interface and routing interface in the same zone. 

Strict IP: if source interface and routing interface exactly the same.

Spoof IP is for internal Zone only.