From: Howard C. Berkowitz (hcb@xxxxxxxxxxxx)
Date: Fri Mar 15 2002 - 19:54:17 GMT-3
At 8:05 PM +0000 3/15/02, Brian Lodwick wrote:
>We had a customer that was on our old old network. This network had
>a different AS and addressing. This customer wanted to move to a
>newer solution we offered, but wanted to keep the existing
>addressing structure. This wasn't much an issue, because accoring to
>our policy we were allowed to advertise any customer net above a
>/24, and they had a /22. The old network advertised an aggregate so
>this more specific range was preferred and the transition worked.
>The reason I went into this whole schpeal is that like you said if
>you get addressing space from one of the providers, and you get
>approval to advertise that range out of the other provider as well,
>you will have sort of a primary / secondary solution and will not be
>able to achieve load sharing.
Untrue. Now, both providers MUST agree to it. Let's say there is a
/24 from provider A's space, which comes out of their /16. Provider
B certainly can advertise the /24, although it wouldn't be done in
usual practice without agreement with A.
Now, the subtle point. Once provider A agrees to let provider B
advertise the more-specific, provider A _must_ advertise both the /16
_and_ a /24 for each multihomed customer. Otherwise, as you suggest,
all traffic would take the more-specific advertised by provider B.
>Reason being is the provider you get your addressing space from will
>most likely be advertising to the NAP an aggregate so the other one
>that allows you to advertise the /24 will always be preferred over
>the aggregate. If redundancy is the only requirement you would be
>fine if you had one provider give you addressing space and you
>advertised it out of the other provider as well.
>I wasn't aware you couldn't purchase a /24 from ARIN. I'm not really
>too knowledgeable on that type of thing. I only cut addressing space
>from our nets when needed for our customers. I have never gone out
>and tried to purchase addressing space from ARIN.
"Purchase" really isn't the right word. Allocation is the correct
term for handing out provider-independent address space. ARIN, RIPE
NCC, and APNIC won't just hand out space to anyone that brings them
money; they will need to see a justification and will review your
efficient utilization if you ask for more.
You can multihome to multiple POPs of the same provider, with
provider-assigned address space. See RFC 1998. You can even do this
with PI space and a private ASN, although it's sort of a kludge. See
RFC 2270.
There are also engineered solutions where two providers originate the
same prefix, which is technically an "inconsistent AS" but is not
uncommon and doesn't really create problems.
The address registries also make no guarantees if your address space
will be globally routable. There is a trend to reduce the number of
prefix length filters, but that also means the current routing
architecture will run out of steam in 4-8 years. I'm involved in the
Internet Research Task Force effort that's just starting to look at
"what comes after the BGP architecture."
>
>BTW I have a neat HSRP & BGP redundancy solution to fix the downfall
>of using this combination if you'd like to hear about it?
>
>
>>From: Vincent Lee <mcne95@yahoo.com>
>>Reply-To: Vincent Lee <mcne95@yahoo.com>
>>To: Brian Lodwick <xpranax@hotmail.com>, wade.edwards@powerupnetworks.com
>>CC: ccielab@groupstudy.com
>>Subject: RE: OT: Change primary ISP from PacBell to Quest
>>Date: Fri, 15 Mar 2002 11:09:07 -0800 (PST)
>>
>>Where can we apply for a class C IP address? ARIN
>>only sell a larger block IP address. I believe if we
>>want multihomed with different ISPs (AS), we need to
>>setup BGP with both ISPs as peering.
ARIN and the other registries will generally allocate /24 if you can
show them contracts with two upstream providers, at least 50%
utilization of your current address space, and various other
justifications.
You will probably need an AS number as well for general-case
multihoming. There are requirements there. RIPE NCC, for example,
requires that you write out your routing policy in RPSL and put it in
the routing registry; this is optional but recommended for ARIN.
Note that the address and routing data bases are separate.
>>
>>thanks
>>
>>--- Brian Lodwick <xpranax@hotmail.com> wrote:
>>> The organization I work for will only allow it if
>>> the space is /24 or
>>> larger.
>>>
>>> >>>Brian
>>>
>>>
>>> >From: "Wade Edwards"
>>> <wade.edwards@powerupnetworks.com>
>>> >Reply-To: "Wade Edwards"
>>> <wade.edwards@powerupnetworks.com>
>>> >To: "Vincent Lee" <mcne95@yahoo.com>
>>> >CC: <ccielab@groupstudy.com>
>>> >Subject: RE: OT: Change primary ISP from PacBell to
>>> Quest
>>> >Date: Fri, 15 Mar 2002 12:16:17 -0600
>>> >
>>> >To get a true backup you have to apply for your own
>>> address space that
>>> >you can announce to both PacBell and Qwest. If you
>>> are using address
>>> >space from both PacBell and Qwest then they will
>>> not allow you to
>>> >announce their addresses through a different
>>> provider. You can ask if
>>> >they will but this is usually against their routing
>>> policy. So you
>>> >don't need BGP. Just use static routing.
>>> >
>>> >L8r.
>>> >
>>> > -----Original Message-----
>>> >From: Vincent Lee [mailto:mcne95@yahoo.com]
>>> >Sent: Friday, March 15, 2002 11:49 AM
>>> >To: Brian Lodwick; dmadlan@qwest.com
>>> >Cc: ccielab@groupstudy.com
>>> >Subject: Re: OT: Change primary ISP from PacBell to
>>> Quest
>>> >
>>> >We are using the PacBell and already ordered the
>>> Qwest
>>> >Circuit.
>>> >Two perimeter routers configed with HSRP and they
>>> are
>>> >only connect to Pacbell at this moment.
>>> >
>>> >We are going to keep PacBell as secondary with a
>>> >smaller bandwidth. Qwest will be the primary
>>> inbound
>>> >Web traffic.
>>> >
>>> >My first step is asking PacBell and Qwest for AS
>>> >peering info then I'll apply for our own AS from
>>> ARIN.
>>> >
>> > >thanks
>>
>>
>> > > > > Dave
>>> > > >
>>> > > >Vincent Lee wrote:
>>> > > > >
>>> > > > > I am going to setup a redundancy multihomed
>>> BGP
>>> > > > > network with two separate ISPs - PacBell and
>>> > > Quest.
>>> > > > >
>>> > > > > Here is my plan.
>>> > > > >
>>> > > > > 1. setup BGP in our company's perimeter
>>> routers
>>> > > > >
>>> > > > > 2. connect to Pacbell and Quest autonomous
>>> > > system
>>> > > > >
>>> > > > > 3. Change primary DNS server from PacBell to
>>> > > Quest in
>>> > > > > Network Solutions/VeriSign
>>> > > > >
>>> > > > > 4. Change our Web IP address in Network
>>> > > > > Solutions/VeriSign and point smtp relay
>>> > > servers to
>>> > > > > Quest.
>>> > > > >
>>> > > > > Any suggestions are welcome and appreciated.
>>> > > > >
>> > > > > >
>
-- "What Problem are you trying to solve?" ***send Cisco questions to the list, so all can benefit -- not directly to me*** ******************************************************************************* * Howard C. Berkowitz hcb@gettcomm.com Chief Technology Officer, GettLab/Gett Communications http://www.gettlabs.com Technical Director, CertificationZone.com http://www.certificationzone.com "retired" Certified Cisco Systems Instructor (CID) #93005
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