External BGP Controller for L3 Switch BGP routing

David Bass davidbass570 at gmail.com
Mon Jan 16 13:41:44 UTC 2017

Arista has a version of their switches that can handle a full table.  

I think what the OP is asking about though is something like openflow though.  Some have played around with using it to modify the switches routing table based on flows that exist.  The same theory applies in regard to the presentation link provided (we don't need the full table 99%of the time, so just insert what you need). 

Using filters is an "old school" technique that's been around for a long time, and I don't think that's what he's asking.  

> On Jan 16, 2017, at 2:00 AM, Yucong Sun <sunyucong at gmail.com> wrote:
> In my setup, I use an BIRD instance to combine multiple internet full
> tables,  i use some filter to generate some override route to send to my L3
> switch to do routing.  The L3 switch is configured with the default route
> to the main transit provider , if BIRD is down, the route would be
> unoptimized, but everything else remain operable until i fixed that BIRD
> instance.
> I've asked around about why there isn't a L3 switch capable of handling
> full tables, I really don't understand the difference/logic behind it.
>> On Sun, Jan 15, 2017 at 10:43 PM Tore Anderson <tore at fud.no> wrote:
>> Hi Saku,
>> https://www.redpill-linpro.com/sysadvent/2016/12/09/slimming-routing-table.html
>>> ---
>>> As described in a prevous post, we’re testing a HPE Altoline 6920 in
>>> our lab. The Altoline 6920 is, like other switches based on the
>>> Broadcom Trident II chipset, able to handle up to 720 Gbps of
>>> throughput, packing 48x10GbE + 6x40GbE ports in a compact 1RU chassis.
>>> Its price is in all likelihood a single-digit percentage of the price
>>> of a traditional Internet router with a comparable throughput rating.
>>> ---
>>> This makes it sound like small-FIB router is single-digit percentage
>>> cost of full-FIB.
>> Do you know of any traditional «Internet scale» router that can do ~720
>> Gbps of throughput for less than 10x the price of a Trident II box? Or
>> even <100kUSD? (Disregarding any volume discounts.)
>>> Also having Trident in Internet facing interface may be suspect,
>>> especially if you need to go from fast interface to slow or busy
>>> interface, due to very minor packet buffers. This obviously won't be
>>> much of a problem in inside-DC traffic.
>> Quite the opposite, changing between different interface speeds happens
>> very commonly inside the data centre (and most of the time it's done by
>> shallow-buffered switches using Trident II or similar chips).
>> One ubiquitous configuration has the servers and any external uplinks
>> attached with 10GE to leaf switches which in turn connects to a 40GE
>> spine layer with. In this config server<->server and server<->Internet
>> packets will need to change speed twice:
>> [server]-10GE-(leafX)-40GE-(spine)-40GE-(leafY)-10GE-[server/internet]
>> I suppose you could for example use a couple of MX240s or something as
>> a special-purpose leaf layer for external connectivity.
>> MPC5E-40G10G-IRB or something towards the 40GE spines and any regular
>> 10GE MPC towards the exits. That way you'd only have one
>> shallow-buffered speed conversion remaining. But I'm very sceptical if
>> something like this makes sense after taking the cost/benefit ratio
>> into account.
>> Tore

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