Internet Edge Router replacement - IPv6 route table size considerations

Owen DeLong owen at
Thu Mar 10 16:58:55 CST 2011

On Mar 10, 2011, at 1:01 PM, Blake Hudson wrote:

>> My concern is trying to find a router (within our budget) that has room for growth in the IPv6 routing space.  When compared to the live table sizes that the CIDR report and routeviews show, some can't handle current routing tables, let alone years of growth.  BGP tweaks may keep us going but I can't see how 16k or fewer IPv6 routes on a router is going to be viable a few years from now.
>> Thank you,
>> Chris Enger
> Does anyone think that the IP6 routes will grow like IP4 routes have?
> With most organizations being granted IP6 /32's - e.g. something larger
> than they could ever use -  wouldn't you expect the number of routes to
> be much much fewer than with today's IP4 setup where even small
> organizations often have multiple routes, and big organizations may have
> hundreds?
Most end user organizations should be receiving a /48 per end site.

Most ISPs should probably get something larger than  a /32 unless they
have fewer than 48,000 customers or so.

The number of prefixes per ASN in IPv6 should probably end up around 1.75.
The current average in IPv4 is approximately 10.

> When sizing routers, shouldn't we be looking at the number of expected
> ISPs (AS's) active on the Internet, within the anticipated lifetime of
> the router? If so, then the question becomes how many is that - 16k
> seems very shortsighted, 128k maybe overkill (at least, for now). We're
> currently at 37k AS's ( So 64k IP6
> routes would probably be the minimum that I would accept on a new single
> homed router. If I expected to act as a carrier, or participate in equal
> cost BGP routing on a multi-homed router, I'd need more.
16k is extraordinarily short-sighted. It will be at least 30,000 just to
duplicate the current IPv4 network. 128k is probably reasonable
headroom. I wouldn't want to go any smaller, given the likelihood
of some multiple slightly greater than 1 prefix per AS.

> As IP6 adoption grows, and networks start to de-aggregate, 128K IP6
> routes sound like a better number for the second or third revision of
> "IP6 ready" gear that would be purchased in 5+ years.
I would say 128k is more like the minimum for anything I would buy


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