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SG300-28P - TCAM IPv4 Route entries - Formula for calculation of expected growth

Hi All,


We've got a 7 site business which has from 2 to 6 SG300-28P switches (depending on size) at each site with a mixture of firmware versions. We have one main Layer 3 switch at each site which is the gateway for the voice and wifi VLAN's. Recently at one of the bigger sites we had our cable guy change the patching from a daisy chain configuration (due to lack of physical network cabling around the building) to the hub and spoke. What we then found was new phones/laptops etc unable to access the network or receive a DHCP address. We found that the default TCAM setting of 128 IPv4 routing was maxed out. I was wondering if this hub/spoke configuration caused the bump in tcam entries? I've now adjusted this figure to 300 and rebooted overnight so I'm hoping this solves the issue as we probably have around 50 computers, 80 wifi devices (own VLAN) and 40 phones (own VLAN) at this site  - What I wanted to know was how to I anticipate what the TCAM entries will be as numbers increase? I'm a bit red faced with the client as we had been thinking the issue experienced with DHCP, DHCP Relay or the MPLS network as opposed to hitting maximum capacity with the switch. I know in the past on these forums people mention these switches shouldn't go past 100 user sites but that to me is a general rule as opposed to theoretical limit - What I want to know is how I hit the 128 IPv4 route limit (what is the calculation method) and I can then plan accordingly in future.


Thanks Everyone

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