From: Peter Van Oene (pvo@xxxxxxxxxxxx)
Date: Tue May 08 2001 - 17:28:40 GMT-3
I would tend to think this stems from RR's assignment policies (ARIN in this ca
se). If things are properly adhered to, most larger organizations (read major
SP's) will recieve B space, and smaller will recieve C space. Hence, outside o
f breaks from policy, these addresses should originate in their aggregate form
and be controlled as such.
Pete
*********** REPLY SEPARATOR ***********
On 5/8/2001 at 1:06 PM Dan wrote:
>This is correct. A /24 from Class C space has a better chance of being
>propagated than a /24 from A or B space.
>
>This is Verio's policy which is similar to the policy of "many" other
>ISPs:
>
>Outbound Announcements:
>We will not announce any prefix larger than /24 (regardless of whether it's
>A, B, or C space) to our Peers.
>
>Inbound Announcement from our Peers (this does not apply to "Customer"
>Peerings):
> a.. We accept /20 and shorter in the 24/8, 61/8, 62/8, 63/8, 64/8, 65/8,
>and 66/8 address space.
> b.. In the traditional Class A space (i.e., 0/1), we accept /19 and
>shorter, with the exceptions specified above.
> c.. In the traditional Class B space (i.e., 128/2), we accept /16 and
>shorter.
> d.. In the traditional Class C space (i.e., 192/3), we accept /24 and
>shorter.
>
>While we will allow BGP customer's to announce "any" prefix /24 or shorter,
>other ISPs may filter these announcements and not listen to them, the same
>way that we will not listen to certain announcements that do not comply
>with
>our above policy.
>I always warn my customer of this when setting up peering sessions. Some
>tell me that they have no problems routing a /22 from Class B space, but I
>always forewarn them.
>
>Please don't ask me why (I don't entirely agree with all of it myself).
>
>-Dan Pontrelli
>
>
>> Cisco told me today that a /24 drawn from Class C space
>> has a better chance of being propogated throughout the Internet
>> than a /24 taken from Class B space. Anyone disagree with that?
>> Can anyone recommend a good source of info on this. Ive checked
>> Halabi.
>>
>> I came across a good reference during my quest www.traceroute.org
>> Unfortunately, it doesnt offer plain answers to my questions.
>>
>>
>> -----Original Message-----
>> From: gb@ms.mine.nu [mailto:gb@ms.mine.nu]
>> Sent: Friday, April 27, 2001 1:58 PM
>> To: Charlie Winckless; 'Murphy, Brennan'
>> Cc: ccielab@groupstudy.com
>> Subject: Re: real world BGP question
>>
>>
>> Currently on a US basis a /24 would generaly work. Internationaly
>(Europe)
>> most providers would filter out anywhing longer then /20.
>>
>>
>> ----- Original Message -----
>> From: "Charlie Winckless" <CharlieW@netarch.com>
>> To: "'Murphy, Brennan'" <Brennan_Murphy@nai.com>
>> Cc: <ccielab@groupstudy.com>
>> Sent: Friday, April 27, 2001 1:18 PM
>> Subject: RE: real world BGP question
>>
>>
>> > I used to work for VERIO. At that time they would not
>> > router smaller than /19 on their backbone.
>> >
>> > This may have changed.
>> >
>> > > -----Original Message-----
>> > > From: Murphy, Brennan [mailto:Brennan_Murphy@nai.com]
>> > > Sent: Friday, April 27, 2001 10:46 AM
>> > > To: 'Michelle T'; 'ccielab@groupstudy.com'
>> > > Subject: RE: real world BGP question
>> > >
>> > >
>> > > I guess that is my real question: what is the longest prefix that
>> > > is exchanged among/between major carriers.
>> > >
>> > > The real world example here is what if you had 4 server farms
>> > > answering
>> > > to one DNS name: ftp.foo.com You have Round Robin DNS running
>> > > round trip times to match a user with their nearest server farm....
>> > > so it sends back the closest/fastest IP. The question is, how
>> > > big do those
>> > > subnets for the server farms have to be in order to be maximally
>> > > advertised throughout the internet?
>> > >
>> > > So, I've seen two answers in this thread /20-21 or /24. I wonder
>> > > where I could find the real answer? Maybe Halabi has a link in the
>> > > back of his book to an organization that maintains info such as
>> > > this.
>> > >
>> > > Any more input is greatly appreciated. Thanks to all who have
>> > > responded.
>> > > I figured this question was a relavant BGP question relating
>> > > our studies
>> > > to an actual scenario.
>> > >
>> > >
>> > >
>> > > -----Original Message-----
>> > > From: Michelle T [mailto:mtruman@mn.mediaone.net]
>> > > Sent: Friday, April 27, 2001 12:06 PM
>> > > To: Murphy, Brennan; ccielab@groupstudy.com
>> > > Subject: RE: real world BGP question
>> > >
>> > >
>> > > /24 is the longest prefix you will see accepted by nearly any
>> > > carrier out
>> > > there. Many will only accept /20 or /21. All perform
>> > > aggregation to some
>> > > degree, though exception routing is allowed to send the /24's
>> > > (/23, /22,
>> > > etc) out to the ISP peers when the customer is multi-homed two
>diverse
>> > > carriers.
>> > >
>> > > I can tell you that I work for a Tier 1 ISP and we accept
>> > > longer prefixes
>> > > for many customers who are multi-homed just to us. They use
>> > > the various
>> > > subnets as a simple method of controlling inbound traffic
>> > > distribution, to
>> > > enact policy, etc...
>> > >
>> > > Many times we see multi-homed (dual-ISP) customers advertise
>> > > an aggregate
>> > > /16 or longer and also advertise /24's for the same reaason (policy,
>> > > distribution, etc).
>> > >
>> > > Michelle Truman
>> > >
>> > >
>> > > -----Original Message-----
>> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf
>Of
>> > > Murphy, Brennan
>> > > Sent: Friday, April 27, 2001 10:28 AM
>> > > To: 'ccielab@groupstudy.com'
>> > > Subject: real world BGP question
>> > >
>> > >
>> > > What is the smallest subnet that major carriers will exchange with
>one
>> > > another? /24..../26.../27?? I know that the real issue is
>> > > the size of
>> > > the route table.
>> > >
>> > > I'm just wondering about the reallity of scenarios that
>> > > Habali describes
>> > > where an institution advertises an aggregate with specific subnets.
>> > >
>> > > I know that when you're multi-homed to a carrier, that carrier will
>> > > sometimes
>> > > take your /26 and /27 nets to help route inbound traffic but
>> > > that carrier
>> > > will not advertise those nets to its neighbors.....at least
>> > > thats what I've
>> > > heard.
>> > >
>> > > Anyone have any real world experience with this? Or is there a URL
>> > > I could read up on?
>> > >
>> > > Thanks,
>> > >
>> > > BM
>> > > **Please read:http://www.groupstudy.com/list/posting.html
>> > > **Please read:http://www.groupstudy.com/list/posting.html
>> > **Please read:http://www.groupstudy.com/list/posting.html
>> **Please read:http://www.groupstudy.com/list/posting.html
>**Please read:http://www.groupstudy.com/list/posting.html
**Please read:http://www.groupstudy.com/list/posting.html
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