[c-nsp] RAM for 4431 with full BGP table?

[Adam Greene]

Hi all,

 

I am trying to figure out if a 4431 can accommodate a full BGP routing table
with its default 4GB RAM or if it needs 8GB.

 

Our current benchmark is a 2921 router with 2.5GB RAM:

 

Cisco CISCO2921/K9 (revision 1.0) with 2506752K/114688K bytes of memory

 

With a full routing table, it is only using about 839MB of RAM:

 

ROUTER#sh mem

                Head    Total(b)     Used(b)     Free(b)   Lowest(b)
Largest(b)

Processor   3D52CDE0   2350969276   839257740   1511711536   1237731724
643241260

      I/O    9000000   117440512    18382712    99057800    98987952
98649340

 

(By the way, I would not recommend running a 2921 with a full BGP routing
table since the CPU starts to buckle when throughput also approaches 100M,
in my experience).

 

By default, the 4431 comes with 2 GB for the data-plane and 4 GB for the
control-plane. I would think this would be sufficient for a full BGP table,
but the opinions I've seen out there appear to be conflicting. For example:

 

https://supportforums.cisco.com/t5/wan-routing-and-switching/maximum-bgp-tab
le-size-in-isr-4551-4331-with-standard-data-plane/td-p/2816329

 

Cisco itself states
(https://www.cisco.com/c/en/us/products/collateral/routers/4000-series-integ
rated-services-routers-isr/white-paper-c11-734550.html#_Toc424889858) that
"All Cisco 4000 platforms support a full Internet routing table (500,000
prefixes) @ 8-GB DRAM."

 

It's sounding to me like 8GB would be advisable.

 

Wondering if anyone out there has real-world experience to share.

 

BTW, in our case, we have limited ACLs and no NAT, but do have about 80 QoS
policies also consuming resources (though I think that would impact CPU more
than RAM).

 

Thanks,

Adam