Date: Sat, 18 Jul 2020 08:32:15 -0700 (PDT) From: "Rodney W. Grimes" <freebsd-rwg@gndrsh.dnsmgr.net> To: abb@abbon.net Cc: "Alexander V. Chernikov" <melifaro@ipfw.ru>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: How to increase the size of the MAC address caching table? Message-ID: <202007181532.06IFWFG9031292@gndrsh.dnsmgr.net> In-Reply-To: <48aedb01-d705-296a-85ba-e2dbf43c4ba2@abbon.net>
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> 18.07.2020 16:16, Alexander V. Chernikov ?????: > > 18.07.2020, 13:56, "Alexandr Baryshnyev" <abb@abbon.net>: > > > > Hello everybody. > > > > ???I have about 1,500 devices on the network, but in fact the MAC address table on the central router running Freebsd > > 12.0 never contains more than 1000 with small cached records. In the network, there are short-term random interruptions > > between different hosts and the router. The connection to the Internet on different computers in the network is lost for > > a short time. No apparent cause of these breaks was found. > > > > How often does this happens and what is the average "short-term" duration? > > I'd look into route -n monitor (don't remember if arp state reporting was merged into 12.0) and try to tcpdump arp > > traffic to get understanding what's happening here. > > Also: does this router perform TCP termination of the flows toward Internet? > > Breaks occur for no apparent reason. If you take one computer on the network, it first works without problems for a long > time, then it suddenly starts breaks: one minute there is no connection, then there are a few minutes and so on in a > circle. After a while (sometimes from one to three days) normal operation on this computer resumes, but the problem goes > to another computer on the network and there is the same thing that happened on the previous computer. Since we are talking arp I am going to assume no routing protocol is active on this collision domain. Please correct me if I am wrong about this. What is the switching topology of this 1500 node collision domain? Is it possible leaf switches are occasionally experiencing a MAC table overflow? How are IP addresses assigned, if by DHCP what are the lease lengths? Is it possible an IP is getting recycled while the node still thinks it has a valid lease? > > > ???There is a suspicion that the MAC address table on the FreeBSD router has a limited size, about 1000 with a small > > record maximum. Is that so? Is it possible to increase the size of this table if it is limited? An internet search was > > not successful. > > > > It's not limited. > > OK, thank you. So we have another cause for our problem. > > > ??Help me, please. > > > > ?> arp -an | grep -ve incomplete | wc -l What are these incomplete entries you filtered out? How many are there and why are the occuring? > > ?????1055 > > > > "Incomplete" are still entries in the per-interface mac address table. What's the size with incomplete ones? > > > arp -an | wc -l > 1183 > > ifconfig bridge0 addr | wc -l > 1214 You are using FreeBSD as a transparent bridge for 1214 nodes? I know I only asked a lot of questions but hopefully some of the answers might provide an insight into what is going wrong. > ? Thank you. > -- > Best regards, > Alexandr B. Baryshnyev, e-mail: abb@abbon.net -- Rod Grimes rgrimes@freebsd.org
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