Performance of Cisco 3750 Layer 3 switch

15 pts.
Cisco 3750
Cisco switch configuration
Cisco switches
L3 Switches
Layer 3 switches
Switch configuration
Hi guys, I have a cisco 3750 series L3 switch. It can currently handle 3GB of L2 traffic with no problem, but when faced with 40MB of L3 traffic, CPU utilization shot so high that I can't even telnet to the switch. Could anyone enlighten me please? Thanks in advance!!

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  • Troy Tate
    How many VLANs? How much of the traffic is destined for devices local to the switch?
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  • Bluezerk
    Thanks for the quick reply :) Currently there are 2 VLANS from a router to this switch and the amount of traffic that is destined for a device local to the switch is the 40MB stated in the question. This 40MB is obtained by capturing traffic volume on the VLAN on the router. Could it be possible that the IOS is out-of-date or is there something I missed out? It doesn't make sense for 40MB of traffic to spike the CPU utilization, even if its Layer 3 traffic. Thanks!!
    15 pointsBadges:
  • BlankReg
    As no-one replied to your additional info, I will have a try ;-) You are right, this should not cause the symptoms you are seeing. The capture, is this done by port mirroring, because that does impact on the CPU ? If it is L2 or L3 traffic does not make much difference, as only the first packet is routed (processed by the CPU) and the rest are switched, that is why a L3 Switch is MUCH faster than a router. If you have a basic diagram, and put on there what exactly you are doing with the captured traffic, that would really help. Also a copy of the config (remove any passwords before posting) would help as well. The original answer was a good idea, try a newer IOS version, some bugs do cause strange effects.
    12,325 pointsBadges:
  • Snapper70
    Do you have any "fancy features" configured that might be breaking the L3 switching capabilities? - secondary addresses on interfaces - ACL's - special QoS processing Also, what KIND of traffic is it? Specs often include a switched bandwidth throughput, as well as a "packets per second" rate. If all of your traffic is small packets, you may not achieve the same routed throughput.
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