Diagnostics ARP Table 504 Nginx Gateway Timeout

stephenw10

It will it you have enabled this:

Active Network Discovery

Toggle the periodic discovery of network devices using multiple techniques that include ARP scan, MDNS and SSDP.

That's not enabled by default.

johnpoz

Nor should it be enabled on your wan interface ;)

manicmoose

Yep, I get all that.

As mentioned, I hadn't altered the ntopng config for ages, so I don't think that was it - but I've blown away the config now so I can't check.

Nevertheless, it's solved so that's all I care about.

lddj9090

@manicmoose
Thanks for the information, unfortunately wasn't able to check in for a week.

I have uninstalled ntopng, but still got a long waiting time to see the ARP entries. Will do a tcpdump to check further.

johnpoz

did flush the cache? The items would still be there for 20 minutes even if you uninstall what was arping for them.

lddj9090

@lddj9090
How can i clear the arp cache on pfsesne, all at once?

lddj9090

@johnpoz

2-5 minutes.

johnpoz

arp -d -a

or from the gui click the clear arp table.

lddj9090

@johnpoz

Cleared the cache and tried again, still spinning for ages and timeout. Could "snort" be somehow involved?

johnpoz

You need to figure out why your wan has anything it.. Have gone over why there should be nothing in your wan network in your arp cache other than your gateway..

NOTHING should just be arping for every IP on a network.. especially our wan.. So there is something you set to arp, or some other reason.

You need to sniff on your wan and figure out what - are you arping, is it gratuitous arps? etc..

Out of the box pfsense with any package installed shouldn't be arping neither your wan network your lan side networks.. It would have to be some setting you did.. Like the ntop setting for network discovery.

lddj9090

@johnpoz
Alright, I will investigate further and talk back to you later. Thanks for the support so far!

stephenw10

@lddj9090 Do you actually have WAN side ARP entries with public IPs?

Are they eventually being resolved by reverse DNS?

Could a completely different problem than @manicmoose had.

Steve

jimp

Last time someone was seeing ARP for random hosts on WAN it was from having their subnet mask on the WAN interface set to something ridiculous like 0 instead of what it should have been (e.g. 24, 29, etc.)

If your WAN is set to a static address, double check your IP address and subnet mask settings.

Whatever is upstream may be answering ARP for anything with its own MAC. That's unusual but not unheard of.

lddj9090

@stephenw10

As far as I am aware, there aren't any public IP in my ARP output.

Here is a snippet of the ARP -a output: arp_snippet_pfsense.txt

We do have high availability sync enabled. As well as a bunch of Virtual IPs (CARP). Even though they all seem to be configured correctly, could that cause something unexpected?

lddj9090

@jimp

I double-checked the WAN Interfaces static address settings, they are all setup correctly.

johnpoz

And how many entries in your arp table? 1000's ??

lddj9090

@johnpoz
254

johnpoz

Then I doubt your problem is related to what the other poster was seeing in slow downs do to trying to resolve public IP names.

Is pfsense not dhcp or dns for this network - where resolving names could be hindered, for ptr?

lddj9090

@johnpoz said in Diagnostics ARP Table 504 Nginx Gateway Timeout:

hindered

Pfsense is DHCP for certain networks, not for all though. Also pfsense handles DNS request from our internal DNS server, so we can use DNS blocklists.

Pfsense DNS Override has active settings for some domains. Could there be an issue?

johnpoz

how long does it take to display your arp -a table?

from a cmd line? Where @stephenw10 was saying there could be a delay in the table being displayed is lots and lots of IPs in the mac that could not resolve, or take a while to resolve via external dns because they were public, and would do a public PTR query for their names.

If you have directly attached network to pfsense, so it has devices in its mac table - but the dns for these is somewhere downstream or upstream that pfsense has a problem resolving - then guess this could cause a delay in the output of your mac address table. Which could cause a timeout in the gui, etc.

But with only a few hundred entries and local dns, etc.. I don't see how that could be a problem.. When from say ssh you do a arp -a for your arp table how fast does it display?