topic Re: Blacklisting Workstations? in General Topics

Blacklisting Workstations?

Luke_R — Wed, 22 Jan 2020 21:23:11 GMT

Sorry if this is a dumb question, I'm still a bit new to PA.

I've recently had a case where a few workstations cannot access anything beyond the local network. A trace shows that they can reach their default GW, but not the next hop, which is the PA.

As a workaround, I found that changing their IP address resolved the issue. I then found that if another workstation got the old IP through DHCP, they wouldn't work either. For now I've excluded the IP's from the range.

I'm wondering if something on the PA could have seen a threat coming from these IP's, and blacklisted them. Is there any troubleshooting you would recommend in a case like this?

Here's what I've seen so far:

The traffic log shows a lot of entries with an action of 'allow', but a session end reason of 'tcp-rst-from-server'
Nothing in the threat log
No correlated events

Any suggestions?

Re: Blacklisting Workstations?

kiwi — Thu, 23 Jan 2020 10:14:12 GMT

Hi @Luke_R ,

tcp-rst-from-server : The server sent a TCP reset to the client.

You're seeing traffic logs so your traffic is reaching the FW...

I'd check first if the traffic reaching the firewall is actually egressing out correctly ... if not then check for indicators in the global counters:

https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClTJCA0

Cheers,

-Kiwi.

Re: Blacklisting Workstations?

RobinClayton — Thu, 23 Jan 2020 17:05:05 GMT

'tcp-rst-from-server'

Is this from one server or a whole bunch of them?

Re: Blacklisting Workstations?

Luke_R — Thu, 23 Jan 2020 20:38:08 GMT

There were a few different ones. Not a lot though, but I'm not sure what's normal for this user.

Re: Blacklisting Workstations?

Luke_R — Thu, 23 Jan 2020 20:39:42 GMT

Thanks. Next time this happens I will do the packet capture.

I tried to replicate the issue on my laptop, but I haven't been able to. I haven't heard any reports of this happening to anyone else since I posted this either.

It's possible that the issue was something else, not PA. I'll just have to wait for the next report I guess.