Re: v6 multihoming and route filters

[Iljitsch van Beijnum <iljitsch@muada.com>]

On 4-jul-2006, at 13:48, Marc Blanchet wrote:

> And again, b) is what I'm proposing since the first (personal)  
> version of the draft:
> - filter/do not advertise any prefix longer than /48.

> If we agree on this (filter/do not advertise any prefix longer  
> than /48), than I'll put it back into the draft!

What would be the purpose of filtering at /48?

That allows for 2^45 = 351 trillion prefixes in the routing table,  
which I suspect won't work too well on current routers. And it only  
takes a handful of /32s deaggregated into /48s to inflate the IPv6  
global routing table to a size larger than the current IPv4 routing  
table.

So filtering at /48 really doesn't buy you anything, either you don't  
care and/or you have large routers and then prefixes longer than /48  
won't make much of a difference, or you care and/or you have small  
routers and then /48 is too much already.

And in theory, anycast addresses should be announced into inter- 
domain routing (when the anycast group spans ASes) as /128s... Or  
maybe that one has been removed in an update of the RFC in question,  
not sure.

By the way:

mysql> select count(*) from addrspace where type='ipv6' and num > 35;
+----------+
| count(*) |
+----------+
|      137 |
+----------+

mysql> select country, descr as prefix, num as pfxlen from addrspace  
where type='ipv6' and num > 35 and not descr like "2001:7f8:%" and  
not descr like "2001:504:%" and not descr like "2001:503:%";
+---------+------------------+--------+
| country | prefix           | pfxlen |
+---------+------------------+--------+
| JP      | 2001:7fa::       |     64 |
| HK      | 2001:7fa:0:1::   |     64 |
| KR      | 2001:7fa:0:2::   |     64 |
| JP      | 2001:7fa:0:3::   |     64 |
| TW      | 2001:7fa:1::     |     48 |
| ID      | 2001:7fa:2::     |     48 |
| NZ      | 2001:7fa:3::     |     48 |
| NZ      | 2001:7fa:4::     |     48 |
| CN      | 2001:7fa:5::     |     48 |
| VN      | 2001:7fa:6::     |     48 |
| JP      | 2001:7fa:7::     |     48 |
| KR      | 2001:7fa:8::     |     48 |
| AU      | 2001:7fa:9::     |     48 |
| AU      | 2001:7fa:a::     |     48 |
| AU      | 2001:7fa:b::     |     48 |
| AU      | 2001:7fa:c::     |     48 |
| AU      | 2001:7fa:d::     |     48 |
| AU      | 2001:7fa:e::     |     48 |
| ID      | 2001:7fa:f::     |     48 |
| CN      | 2001:7fa:10::    |     48 |
| US      | 2001:500::       |     48 |
| US      | 2001:500:1::     |     48 |
| US      | 2001:500:2::     |     48 |
| US      | 2001:500:3::     |     48 |
| US      | 2001:500:4::     |     48 |
| US      | 2001:502:100e::  |     48 |
| US      | 2001:502:2eda::  |     48 |
| US      | 2001:502:4612::  |     48 |
| US      | 2001:502:7a71::  |     48 |
| US      | 2001:502:ad09::  |     48 |
| US      | 2001:502:cfb5::  |     48 |
| US      | 2001:502:d399::  |     48 |
| US      | 2001:502:f3ff::  |     48 |
| BR      | 2001:12f8::      |     48 |
| AR      | 2001:12f8:1::    |     48 |
| CO      | 2001:12f8:2::    |     48 |
| MX      | 2001:12f8:4000:: |     48 |
+---------+------------------+--------+
37 rows in set (0.16 sec)


> =========
> IPv6 book: Migrating to IPv6, Wiley, 2006. http://www.ipv6book.ca

Mine is published by Apress, see http://www.runningipv6.net/  :-)