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tcroghan
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ipv4 neighbor table overflow

Wed Dec 12, 2018 10:01 pm

I keep getting this error in my logs "ipv4 neighbor table overflow, please consider increasing max-neighbor-entries"

6.43.7 firmware (Although I was seeing this less frequently on 6.43.3 the previous firmware, by less frequently I would see this in the logs maybe 6-10 times in a day.)

The router was left at the default max-neighbor-entries of 8192, but I have tried changing it to higher and lower numbers with no change. When I try increasing the number there is sometimes a delay before the error reoccurs.

At the moment I am getting this error in groups of 6-8 that all come in within a second and each group will happen several times a minute. Sometimes I will only get the error alone though, no idea what the correlation is... Sometimes I only get a few single errors over several minutes to an hour.

Neighbor entries are at 140, sometimes 139, though no correlation there it seems.
ARP table is at 306 with little variance.

Nothing new connected to the router, maybe a customer router?

There does not seem to be a correlation between neighbor entries expiring and the log occurring.

This tower is pretty similar, in config and hardware connected to it, to most of the rest of my network and none of my other routers are doing this.

More then willing to provide any other information if it might help.

Thanks ahead of time for the help.
 
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sebastia
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Re: ipv4 neighbor table overflow

Thu Dec 13, 2018 5:30 pm

Hi
Do you even use it? Just disable altogether...
 
tcroghan
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Re: ipv4 neighbor table overflow

Thu Dec 13, 2018 6:25 pm

We don't use it, but disabling did not stop the errors from occurring. I apologize, I should have posted this fact as well, we have tried so many different things and it slipped my mind.

By "disable" I mean we turned off neighbor discovery by IP > Neighbors > Discovery Settings > Interface "None"
ip neighbor discovery-settings set discover-interface-list=none is the command I used.

If there is another way that I am unaware of please correct me.
 
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sebastia
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Re: ipv4 neighbor table overflow

Thu Dec 13, 2018 9:01 pm

that log message needs to be corrected :-D

just googled max-nei... => https://wiki.mikrotik.com/wiki/Manual:IP/Settings => ARP table setting

Since you increased it without effect and the actual sizes are nowhere near the limit -> support ticket
 
tcroghan
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Re: ipv4 neighbor table overflow

Thu Dec 13, 2018 10:38 pm

Sigh, I hate to bother them, it feels like it is a problem on my end especially because none of my other routers are doing the same thing.

Thank you for the help. I will try to report back with what Mikrotik says.
 
tcroghan
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Re: ipv4 neighbor table overflow

Wed Dec 19, 2018 2:34 am

Have not heard back from Mikrotik Support yet, but I have found that by turning off Route Caching it stops my "ipv4....." error from occurring, at least as frequently, only been 30 minutes, but turning it back on immediately causes the error to re-occur.

The weird thing is, "ip route cache print" shows only ~17K entries and a maximum of 262144. On my other routers I see up to 30K entries. So I still feel like I am doing something wrong...

I also noticed that many IPs that I try to ping give me the error message "105 (No buffer space available)" which I have never seen before and my google searches have not lead me to any informative information.

Ram is ~75% free
Drive is ~50% free
Processor is not very busy ~20% total and max 50% on any one core at a time...
CCR 1009-7G-1C-1S+ (tile)
If any of this information might help...

Any ideas would be most appreciated.
 
tcroghan
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Re: ipv4 neighbor table overflow

Wed Jan 02, 2019 9:19 pm

I have found that turning off "Route Caching" under IP Settings kills the error from popping up in the logs. The downside to this solution is that I loose Fast Path, which isn't terribly important at the moment because the bandwidth through the tower is lower then my average and the router can handle everything else.

Mikrotik support is helping me with my bridge config, though nothing we have tried there has stopped the error so far. (Removing unnecessary bridges and turning off "Use-IP-Firewall")

I will try to remember to report back if we find anything else...
 
Azendale
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Re: ipv4 neighbor table overflow

Sun Dec 22, 2019 6:23 am

Did Mikrotik support ever figure out what was causing it, or did you just stay in a config that didn't trigger the issue by turning the route cache off?
 
GREG3f
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Re: ipv4 neighbor table overflow

Mon Jan 13, 2020 5:12 pm

Yes, please update this thread... I have the same issue and looking for a solution.

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