[c-nsp] association between TCAM usage and CPU load in L3 switch

[Martin T]

Mark, Dimitris,

at the time of the test, this L3 switch was not acting as router. In
other words it was performing no route lookups, but still the CPU load
was ~100% when all the unicast IPv4 TCAM entries were exhausted.



regards,
Martin

On 2/5/14, Dimitris Befas <dimitris.befas at gmail.com> wrote:
> Maybe the router does process switching for the traffic while the
> corresponding table is full. Maybe you can check with sh int x/x while the
> cpu is overload.
> On Feb 5, 2014 5:56 PM, "Martin T" <m4rtntns at gmail.com> wrote:
>>
>> Hi,
>>
>> I have a Cisco ME-3600X-24FS-M switch which supports up to 20000
>> unicast IPv4 prefixes with SDM profile in use. If I announce full BGP
>> table to this switch and exhaust all the TCAM available for unicast
>> IPv4 prefixes:
>>
>>
>> ME3600X#sh platform tcam utilization ucastv4
>> Nile Tcam Utilization per Application & Region:
>> ES == Entry size == Number of 80 bit TCAM words
>> ==================================================================
>> App/Region            Start  Num Avail  ES    Used Range  Num Used
>> ==================================================================
>> UCASTV4                   0     20480   1
>>     nile0                                                    20000
>>     nile1                                                    20000
>>
>>
>> ..then CPU load will be around 100%:
>>
>>
>>       111 111
>>       00090009     1             1  1         1
>>       000900099999609899888998999099399999999909788888889888998899
>>   100 #######*
>>    90 #######*
>>    80 #######*
>>    70 #######*
>>    60 ########
>>    50 ########
>>    40 ########
>>    30 ########
>>    20 ########
>>    10 ########**************************************************
>>      0....5....1....1....2....2....3....3....4....4....5....5....6
>>                0    5    0    5    0    5    0    5    0    5    0
>>                CPU% per minute (last 60 minutes)
>>               * = maximum CPU%   # = average CPU%
>>
>> According to "sh ip route summary", RAM usage for BGP was around
>> 85MiB. What exactly is causing such high CPU usage? I should have run
>> "sh processes cpu sorted 5min" during the high CPU usage, but forgot
>> to do so.
>>
>>
>>
>> regards,
>> Martin
>> _______________________________________________
>> cisco-nsp mailing list  cisco-nsp at puck.nether.net
>> https://puck.nether.net/mailman/listinfo/cisco-nsp
>> archive at http://puck.nether.net/pipermail/cisco-nsp/
>