ISP customer assignments

Chris Adams cmadams at hiwaay.net
Fri Oct 16 00:17:54 UTC 2009


Once upon a time, Michael Dillon <wavetossed at googlemail.com> said:
> And only the largest ISPs will outgrow a /32 allocation.

This brings up something else I'm trying to figure out.  We're not a
huge ISP; I've got our /32 but I don't see us using more.  We have two
main POPs, each with Internet links, plus a link between the two.  Our
IPv4 allocations are larger than the minimum, so I split our IPv4 space
between the two POPs and avertise a smaller block out of the smaller of
the two POPs.

This has worked okay and handles the POP-to-POP link going down; when
that happens, our POP-to-POP traffic (not a large precentage of our
traffic) goes across our Internet connections, but Internet traffic for
each POP goes to directly to the POP.

With IPv6, we've got our single /32.  From what I understand, if I try
to advertise a /33 from the smaller POP, many (most?) will drop it (if
my upstreams even take it).  If I advertise the /32 from both routers,
when that link goes down, my IPv6 traffic will be pretty much hosed.

Is there any good solution to this?  I don't expect us to fill the /32
to justify expanding it (although I do see ARIN appears to have left
space for up to a /29; I guess that's their sparse allocation policy?).

I guess this is traffic engineering, although I'm not deaggregating to
try to control how much goes where, just to ensure connectivity in the
face of failures.  This link has been pretty reliable lately (since the
telco re-engineered it), but it was flakey as hell a while back (when it
went through 7 companies to go between cities 90 miles apart).

-- 
Chris Adams <cmadams at hiwaay.net>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.




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