[j-nsp] System board memory expansion on M7i

[Rubens Kuhl Jr.]

On 11/1/07, Nicolaj Kamensek <nk at accelerated.de> wrote:
> Chris Kawchuk schrieb:
>
> Chris,
>
> > You are correct. cFEB can be either 128 or 256. Again, since the cFEB
> > has all the actual forwarding routes for the router's ASIC's, you mya be
> > able to get away with only 128M for now, but again, as the global
> > routing table gets bigger and bigger, you may run into a limit.
>
> but not because of the DRAM on the FEB. The forwarding-tables itself are
> stored in the SRAM from the FEB and on M7i CFEB it's 8MB in size(maybe
> available with 16mb, I don't know) which can hold up to approximately
> 550.000 routes. The dram only has a copy of the SRAM content.
> But the dram is important for other things like arp entries.

550k IPv4 routes, I guess... so if all IPv4 prefixes get an IPv6
counterpart which has a prefix size twice as IPv4's, that would map to
a 183k (IPv4 + IPv6) routes. Hummmmmmm...

> > Likewise, if you start adding L3VPNs, and add more and more MPLS/VPN
> > routes,  you will run into the 128 Mb limit quickly.
> >
> > Hence, 256M is strongly recommended.
>
> I agree.

Even on a Internet Exchange where there few ARP entries ? A cable
scenario would use thousands of ARP entries... or there are any other
reasons for having 256M on the FEB ?


Rubens