I have a router-on-a-stick scenario where I have 7-8 subnets configured as sub-interface on a gigabit interface on a Cisco 3825 router. Only 3 VLANs are active now.
Say vlan 10=pc data, vlan11=voice, vlan1=apple MAC server.
When an apple PC/laptop connect to vlan10 and need access to vlan1, the performace is horrible, but when apple pc/laptop is moved to the same vlan, performance is way faster.
Gigabit interface on the router shows only 100M utilized.
However I am getting alot of throttles on input queue of the router interface, lots of input queue drops and flushes, and lots of encapulation errors/fragmentaton when I did "show ip traffic".
Seems like a Router-on-a-stick issue but I am not convinced because first of all, the Gigabit is only used 100M, 2nd, maybe the apple pc/laptop is generating a bigger packets than 1500bytes.
Is that because I have too many sub-interfaces? Is there any max number of sub-interface I can have? Is this because of extra Dot1Q tagging which cause a lots of fragmentation/encasulation errors?
I understand that all sub-interface share the same bandwidth, but if I am not even hitting the high water mark, how can I prove that it is a bottle neck?