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L3 ARP table size in sg300-24?


Hi folks,

This is a bit of an odd question because it's about a problem I ran into a year or so ago, but I wasn't aware of these forums at the time, so I thought I'd run it past you all. Unfortunately that means I can't reproduce the problem right now, so it's kind of a theoretical question.

A while ago I tried to deploy an sg300-28 in L3 mode as the "core" switch in our ~70-person office, with static routes across 5 vlans. There were probably around 250 devices on the network in total when you include phones, virtual machines, mobile devices, and so on. Over the deployment weekend things worked fantastic; when everyone came in on Monday, network performance was terribly slow.

So my theory at the time was that the switch's (L3) arp cache was full -- if I pinged  a host on another vlan, the switch would send a new ARP request every  second ping. We scrambled a Linux box to act as a router and disabled the L3 functionality on the switch, and it's been fine since. However, in the months since then, we've observed some STP misconfigurations, which leads me to wonder if it wasn't an ARP table size issue, but rather a topology issue. But moving routing to a different box did solve the problem immediately.

The switch has been fine as our core switch. The MAC table on that switch right now has 358 entries (we've grown since this happened). It was just on level 3 that it wasn't keeping up.

Does this ring a bell? How many arp table entries can an sg300-28 retain?




Tom Watts

Hi Rich, 1 year ago, there was a bug on the and lower firmware where the tcam table would flood and make tcp packet flood through all switch ports. This has been long resolved using the and firmware.

The SX300 switch, in a layer 3 mode, it will hardware switch up to 100 IP addresses. Once above the 100 IP addresses, it gets in to software switching additional requests. The routing module in the switch can report SFFT over flow conditions once that treshhold is reached.

The MAC table can support up to 16000 MAC addresses. The IP table if I remember right should be maximum around 510.

However, this switch is designed for only 100 users. Anything above this can be beyond the capability of the switch.

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-Tom Please mark answered for helpful posts
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