[c-nsp] Best practice - Core vs Access Router

[Tom Sands]

David Freedman wrote:
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> Andy B. wrote:
>> On Wed, Feb 10, 2010 at 7:48 PM, David Freedman
>> <david.freedman at uk.clara.net> wrote:
>>> So, are you checking your interfaces for incrementing drop/error counters?
>>>
>>> Are you seeing any of this when there is the problem occuring?
>>> (clear counters , sh int summ etc..)
>>>
>> I am having input drops all the time, no matter how high or low I set
>> the incoming hold-queue.
>>
>> The OSPF and IBGP interfaces approx. 30 minutes after I cleared the counters:
>>
>> TenGigabitEthernet8/1 is up, line protocol is up (connected)
>>   Input queue: 0/2000/622/622 (size/max/drops/flushes); Total output drops: 0
>>
>> TenGigabitEthernet9/1 is up, line protocol is up (connected)
>>   Input queue: 0/4096/1664/1664 (size/max/drops/flushes); Total output drops: 0
>>
>> TenGigabitEthernet9/2 is up, line protocol is up (connected)
>>   Input queue: 0/4096/1916/1916 (size/max/drops/flushes); Total output drops: 0
>>
>>
>> These links are not congested! Te9/1 is the busiest with maybe 6.5 out
>> of 10 Gig. The other two are below 5 Gig.
> 
> Are these supervisor ports or on a card (i.e 6704/6708?)
> 
> Things I would check:
> 
> - - That I understand 6704 has pathetically small per port buffers


The 6704 looks like the biggest problem in this setup.  We avoid them at 
all cost.


> - - Hold queue input appropriate (for punt to MSFC), usually set to 4096
> for these
> - - No IGP hello padding (if you have large MTU and pad then you must punt
> these big things
> - - Check SPD headroom (show ip spd)
> - - The drops are not being reported on input due to lack of transmit
> buffer on output (i.e to lower speed card), check traffic flows/pps to
> low speed interfaces and adjust buffers appropriately
> 
> Dave.


--------------------------------------------------------------------------------
Tom Sands			  				
Chief Network Engineer				
Rackspace 	    	
(210)312-4391	   	
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