What is the most standard subnet length on internet

Patrick W. Gilmore patrick at ianai.net
Fri Dec 19 22:37:30 CST 2008


On Dec 19, 2008, at 10:48 AM, Joe Greco wrote:

>> As for routing table size, no router which can handle 10s of Gbps is
>> at all bothered by the size of the global table,
>
> ... as long as it isn't something like a Cisco Catalyst 6509 with  
> SUP720
> and doesn't have a PFC3BXL helping out ...
>
> ... or if we conveniently don't classify a Catalyst 65xx as a router
> because it was primarily intended as a switch, despite how ISP's  
> commonly
> use them ...
>
>> so only edge devices
>> or stub networks are in danger of needing to filter /24s.  And both  
>> of
>> those can (should?) have something called a "default route", making  
>> it
>> completely irrelevant whether they hear the /24s anyway.
>
> A more accurate statement is probably that "any router that can handle
> 10s of Gbps is likely to be available in a configuration that is not  
> at
> all bothered by the current size of the global table, most likely at  
> some
> substantial additional cost."

Good point!  I should have said "10s of Gbps and tables associated  
with default-free networks".

Or are there lots of people using 6500s without 3BXLs in the DFZ?  I  
admit I have not audited every router in the DFZ, so perhaps someone  
with factual info can help out here.

If not, then we're back to where we started.  The DFZ isn't worried  
about table size this cycle, and the edges can (should?) have  
default.  I'm sure that will change in a couple years, but everything  
always does.

Oh, and before anyone jumps all over me, I am NOT implying you should  
deaggregate and blow up the table.  Just that 300K prefixes is the DFZ  
is not a reason to start filtering /24s.  Today. :)

-- 
TTFN,
patrick





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