[c-nsp] Cheap BGP router for ~20k prefixes

[Cory Ayers]

While the ASR920 is rated for 20k prefixes, you *can* load a full BGP table, and if you employ BGP selective route download you can hold the full BGP table in memory and choose what's installed in the RIB/FIB.
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-3s/irg-xe-3s-book/irg-selective-download.html

Outputs below are just for information.  This was tested in a lab ONLY.  We definitely would not use this as a border router in the DFZ.  At this point the full table is loaded (about a minute to load) and the ASR920 is stable.
ASR920-4SZ#show ip bgp summ | i memory
536528 network entries using 77260032 bytes of memory
536528 path entries using 42922240 bytes of memory
85706/85706 BGP path/bestpath attribute entries using 13712960 bytes of memory
76431 BGP AS-PATH entries using 3173436 bytes of memory
10 BGP community entries using 240 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 137068908 total bytes of memory

ASR920-4SZ#show memory summary 
                Head    Total(b)     Used(b)     Free(b)   Lowest(b)  Largest(b)
Processor   300CA008   938360592   721711452   216649140   216468264   215970216
 lsmpi_io   680B31D0     6295088     6294120         968         968         968

We aren't employing a download filter at this point, but full table does not get loaded into the RIB.
ASR920-4SZ#show ip route summary 
Route Source    Networks    Subnets     Replicates  Overhead    Memory (bytes)
application     0           0           0           0           0
connected       0           2           0           144         360
static          1           0           0           72          180
bgp 65534       171596      364958      0           38631888    96579720
  External: 536554 Internal: 0 Local: 0
internal        6189                                            21738660
Total           177786      364960      0           38632104    118318920

We do see an error message once a minute about prefixes that can't be installed.
Apr 30 16:23:20.020: %FMFP-3-OBJ_DWNLD_TO_CPP_FAILED:fman_fp_image:  PREFIX 128.73.32.0/24 (Table id 0) download to CPP failed
Apr 30 16:24:20.069: %FMFP-3-OBJ_DWNLD_TO_CPP_FAILED:fman_fp_image:  PREFIX 179.0.152.0/24 (Table id 0) download to CPP failed

ASR920-4SZ#show mls cef exception
                  ^
% Invalid input detected at '^' marker.

Woops, wrong chassis :D

Cory

-----Original Message-----
From: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Gert Doering
Sent: Thursday, April 30, 2015 9:53 AM
To: Dan Brisson
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Cheap BGP router for ~20k prefixes

Hi,

On Thu, Apr 30, 2015 at 10:35:49AM -0400, Dan Brisson wrote:
> Looking for suggestions for a device (switch/router) that can speak BGP 
> and do around 20k prefixes.  The other requirement is minimum 500Mb/s of 
> throughput, which seems to throw a low-end Cisco router out of the mix.  
> I know a 3560 switch can do BGP and wouldn't have the throughput 
> limitations the router lines have.  The cost is probably going to creep 
> up again though when adding Enterprise code for BGP support.

ASR920 or so...  throughput will be fine, price of 2000$ "should" be
achievable (depending on interface and license options).

The caveat, of course, is that it will do exactly 20k prefixe, no more
- so if you might go "up to 30k", it's not the platform 

Or a used 7201 / 7200/NPE-G2...  dirt cheap, 500k+ prefixes, but not much
more than 500Mbit/s throughput.

Your triangle of "number of prefixes / price / throughput" is hitting a
somewhat weak spot in Cisco's portfolio...

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de