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I am not a network engineer, I have very limited knowledge.

background:

We currently have a HP1920-48g switch + others around our building. Originally these were "daisy chainned", the new I.T Director changed this into what he describes as a "spider" like configuration (totally not a tech term im thinking).

Issue:

We have just installed a new telephone IP system, which works with a little computer software called "navigate" recently people coming in later to the building trying to access this would result in a long wait untill there settings loaded etc.

Now we have traced this to a issue with the switch reaching 256 limit in the ARP table.

Question:

Can we increase this limit, ither purchase a new switch (rather not but understand if we must).

Or can we set up something to increase the limit somehow? Unfortunatly I have very little network knowledge. We played around with turning of the Gratuitous ARP but not really sure that we should do this.

  • Switches don't use ARP tables, they have MAC address tables. ARP is used to resolve a layer-3 address to a layer-2 address, but switches don't know or care about layer-3 addresses. Switches do care about which ports have which MAC addresses, so they maintain MAC address tables. This is a very different concept than ARP. – Ron Maupin Jan 25 '17 at 15:51
  • The more common term for "spider" configuration is "star" - it reduces the number of transits data has to make going from what would have been one end of the "daisy-chain" to the other by providing a central node that's only one hop from each access switch, so each access switch is only two hops from every other access switch. – Ecnerwal Jan 26 '17 at 17:30
  • Did either answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. – Ron Maupin Jul 24 '17 at 22:18
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Are you sure this has anything to do with ARP? The 1920 is a layer2 switch and doesn't need to do any ARP.

I'd suspect it has more to do with the subnet size especially the DHCP scope. Once IP address allocation is exhausted - which for the most common /24 subnet size is 256 (or rather 254), you need to enlarge the network. If you've just got this single subnet it's not too hard to do.

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It sadly does have that limit of 256 entries. Perhaps there will be a "Comware 7" upgrade to this switch which will increase that limit, perhaps it won´t. But you can try to disable gratuitous ARP packets learning function (Network -> ARP Management -> Gratuitous ARP)and delete dynamic ARP records.

Hope this will work.

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