From: Hyunseog Ryu (r.hyunseog@ieee.org)
Date: Mon Jul 30 2007 - 20:46:38 ART
Actually IP address requirement for /24 can be meet if customer want to
run BGP with multiple providers.
I believe ARIN make it loosen for /24 reallocation to customer so if
customer run multihomed network with multiple providers, they can get
single /24 from their upstream provider with proof of multihomed network
with multiple providers.
But in most case, it is the resource issue that normal customer don't
want to run BGP.
If customer wants to run BGP, they should have 24X7 staff capable of
maintaining/troubleshooting BGP routing issue.
Also customer router needs more CPU power and memory to run BGP.
For that complexity, why do you want to run BGP and pay additional cost
- even if it's small cost - to ARIN, and spend money to maintain it if
you don't need it ?
Hyun
Ryan wrote:
> Most companies do not get multi-homed with two ISP's. There is generally not
> a need for this and most ISP's have strict address assignment requirements
> that most business's cannot meet. To peer BGP with two ISP's requires a /24
> address block minimum (ISP's will not announce any longer prefix than a /24)
> and companies have a real hard time justifying the usage requirements that
> warrant a /24. Most can only justify a /29 at best which is a typical
> default assignment.
>
> Now, major companies that have a large Internet presence can usually justify
> the address space and can get a second connection with another ISP and their
> own AS number (there are fee's for an AS number, they are not free).
>
> So if your a small business that can not justify the expense of an AS and
> the address space usage to multi-home with two ISP's, your only options are
> to multi-home with the same provide and use a Private AS.
>
> -Ryan
>
>
>
>
>
> On 7/30/07, Gregory Gombas <ggombas@gmail.com> wrote:
>
>> Thanks Scott,
>>
>> Is this what smaller companies typically do?
>> I guess AS path prepending is out of the question considering your
>> service providers will remove the private AS anyway?
>>
>> And finally, with millions of companie out there, I'm shocked that
>> they haven't run out of AS numbers already. What are all these
>> companies doing?
>>
>> On 7/29/07, Scott Morris <smorris@ipexpert.com> wrote:
>>
>>> Heheheh.. In the event of your multihoming, I think your upstream may
>>>
>> be a
>>
>>> little upset to know that you are impersonating them and only
>>>
>> advertising a
>>
>>> small set of routes (e.g. not wanting to be a transit path!).
>>>
>>> So very often we'll have private AS's to use for purposes like this
>>>
>> where
>>
>>> you want to run BGP, but are not multihoming, or simply that you don't
>>>
>> have
>>
>>> provider independent space and even if you are multihoming you aren't
>>>
>> really
>>
>>> advertising anything.
>>>
>>> If you DO have something to advertise, then you need an AS number. I
>>> believe they're only on 49000 something for assignments, so there's
>>>
>> still
>>
>>> room to grow.
>>>
>>> At the same time, they're just wrapping up the 4-byte AS number
>>>
>> extensions,
>>
>>> so no fear of running out now!
>>>
>>> But with the interconnected world of BGP, if you truly have a need to
>>>
>> run
>>
>>> BGP, then you most likely will need your own AS number to do
>>>
>> so. Otherwise,
>>
>>> work with your ISP for private AS assignment, but don't impersonate
>>>
>> them,
>>
>>> they will likely not find the humor in it!
>>>
>>>
>>> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
>>>
>> JNCIE
>>
>>> #153, CISSP, et al.
>>> CCSI/JNCI-M/JNCI-J
>>> VP - Technical Training - IPexpert, Inc.
>>> IPexpert Sr. Technical Instructor
>>>
>>> A Cisco Learning Partner - We Accept Learning Credits!
>>>
>>> smorris@ipexpert.com
>>>
>>> Telephone: +1.810.326.1444
>>> Fax: +1.810.454.0130
>>> http://www.ipexpert.com
>>>
>>>
>>> -----Original Message-----
>>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>>> Gregory Gombas
>>> Sent: Sunday, July 29, 2007 2:05 PM
>>> To: Group study
>>> Subject: Unique AS number when connecting to two different ISP's?
>>>
>>> When connecting to the internet via two different ISP's, why is it
>>>
>> necessary
>>
>>> to have a unique AS?
>>>
>>> What if you simply configured your BGP router with the same AS number as
>>>
>> one
>>
>>> of your ISP's?
>>>
>>> Considering there are only 64511 unique AS numbers, I assume that most
>>>
>> if
>>
>>> not all the AS numbers are already taken. What do companies do in the
>>>
>> case
>>
>>> they cannot get their own AS number and need to multihome?
>>>
>>> Thanks,
>>> Greg
>>>
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