From: Narbik Kocharians (narbikk@gmail.com)
Date: Fri Jun 27 2008 - 21:27:45 ART
If anyone needs the topology i will attach it so you will see what i am
talking about. Marc, Look at the attached topology that i just sent you:
When C2 receives an update, it sends the update to RR-1 and RR-2. RR-2 will
set the cluster-id in the update and send the update to RR-1, RR1 will
reject the update because it sees that the cluster-ids in the update match
its own.
Now Let's say the link between C2 and RR-1 and C1 and RR-2 goes down, now,
C2 gets the update and it sends it to RR-1 and RR-2, RR-2 sets the
cluster-id and sends it to RR-1, and RR-1 will reject the update because it
will see its own cluster-id in the update.
Note half of the cluster has no idea about the update.
But if they had different cluster-ids RR-1 will process the update and send
it to C1.
On Fri, Jun 27, 2008 at 11:29 AM, Marc La Porte <marc.a.laporte@gmail.com>
wrote:
> Narbik,
>
> Why's that?
>
> Marc
>
> On Fri, Jun 27, 2008 at 7:49 PM, Narbik Kocharians <narbikk@gmail.com>
> wrote:
>
>> Basically the cluster-ids should NOT match when you have redundant
>> route-reflectors, for the CCIE lab, you should make sure that they do, but
>> NOT in the real world scenario.
>>
>> On Fri, Jun 27, 2008 at 10:30 AM, Brian McGahan <
>> bmcgahan@internetworkexpert.com> wrote:
>>
>> > Hi Mohamed,
>> >
>> > The BGP router-id comes from the highest loopback address, or if
>> > there is no loopback, your highest interface IP address. The cluster-id
>> > comes from the router-id. In a real design you would always want to
>> > hard code at least the BGP router-id, and possibly the cluster-id
>> > depending on the design. There are certain designs that if your BGP
>> > router-id overlaps with someone else's there could be a problem, such as
>> > if you're doing Anycast RP for multicast. As a general rule OSPF,
>> > EIGRP, and BGP router-id's should always be hardcoded. In the lab exam
>> > if there isn't a requirement *not* to hardcode them, you should set it
>> > to a unique IP address configured on the router.
>> >
>> > HTH,
>> >
>> > Brian McGahan, CCIE #8593 (R&S/SP/Security)
>> > bmcgahan@internetworkexpert.com <mailto:bmcgahan@internetworkexpert.com
>> >
>> >
>> > Internetwork Expert, Inc.
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>> >
>> >
>> > Net Plus wrote:
>> > > Hi Brian,
>> > >
>> > > It means;
>> > >
>> > > Once you set the bgp Router-id, You don't need any Cluster-id, As per
>> > your
>> > > statement, bgp cluster-id is derived from Router-id.
>> > >
>> > > Regards,
>> > >
>> > > Mohamed.
>> > > -----Original Message-----
>> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf
>> Of
>> > > Brian McGahan
>> > > Sent: Friday, June 27, 2008 9:55 AM
>> > > To: cciestruggle; Cisco certification
>> > > Subject: Re: the relation between the route-reflector servers within
>> the
>> > > same bgp cluster id?
>> > >
>> > >
>> > > You should statically set the BGP router ID to a globally significant
>> > > address on the router. The cluster-ID is inherited from router-id
>> > > regardless if you hardcode it or the router-id though.
>> > >
>> > > Brian McGahan, CCIE #8593 (R&S/SP/Security)
>> > > bmcgahan@internetworkexpert.com <mailto:
>> bmcgahan@internetworkexpert.com>
>> > >
>> > > Internetwork Expert, Inc.
>> > > http://www.InternetworkExpert.com <http://www.internetworkexpert.com/
>> >
>>
>> > > Toll Free: 877-224-8987 x 705
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>> > >
>> > > cciestruggle wrote:
>> > >
>> > >> Hello Brain,
>> > >>
>> > >> We do need to have the cluster id on the router reflectors to avoid
>> > >> loops ? right?
>> > >>
>> > >> And further more do we need to explicitly specify the cluster id? the
>> > >> command reference says that it is automatically set to the local
>> > >> router id (of which reflector ?)
>> > >>
>> > >>
>> > >>
>> > >
>> >
>> http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_bgp1.html#
>> > > wp1012377
>> > >
>> > >> Zealot
>> > >>
>> > >> On Fri, Jun 27, 2008 at 3:52 PM, Brian McGahan
>> > >> <bmcgahan@internetworkexpert.com
>> > >> <mailto:bmcgahan@internetworkexpert.com>> wrote:
>> > >>
>> > >> You can, but you don't necessarily have to. Most large scale
>> route
>> > >> reflection designs include a full mesh of peerings between
>> > >> clusters via
>> > >> the route reflectors, but the route reflectors are not clients of
>> > each
>> > >> other. This means that if reflector A peers with reflector B,
>> and
>> > >> reflector B peers with reflector C, reflector C cannot learn a
>> route
>> > >> from reflector A's cluster through B's cluster, because if A is a
>> > >> non-client of B, B cannot advertise an iBGP route from A to C.
>> > >> However
>> > >> if these is a full mesh of non-client iBGP peerings between A, B,
>> > >> and C,
>> > >> reflector C wouldn't need to use B to get to A, since it has a
>> > direct
>> > >> peering.
>> > >>
>> > >> Ultimately for production it depends on your redundancy design.
>> > >> Technically you can have every single router be a router
>> reflector
>> > >> with
>> > >> everyone else beings its clients. You won't cause any routing
>> > loops,
>> > >> since the cluster list prevents this, but instead you'll just
>> have
>> > >> a lot
>> > >> of unnecessary route replication. However when we are talking
>> about
>> > >> update messages in the order of 300,000 routes for the full BGP
>> > table,
>> > >> scalability from a resource management perspective is highly
>> > >> affected by
>> > >> route reflection design.
>> > >>
>> > >>
>> > >> HTH,
>> > >>
>> > >> Brian McGahan, CCIE #8593 (R&S/SP/Security)
>> > >> bmcgahan@internetworkexpert.com
>> > >> <mailto:bmcgahan@internetworkexpert.com>
>> > >> <mailto:bmcgahan@internetworkexpert.com
>> > >> <mailto:bmcgahan@internetworkexpert.com>>
>> > >>
>> > >> Internetwork Expert, Inc.
>> > >> http://www.InternetworkExpert.com<
>> http://www.internetworkexpert.com/>
>>
>> > >> Toll Free: 877-224-8987 x 705
>> > >> Outside US: 775-826-4344 x 705
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>> > >> Live Chat: http://www.internetworkexpert.com/chat/
>> > >>
>> > >>
>> > >> ccie wrote:
>> > >> > Hi experts,
>> > >> >
>> > >> > Assume I have 5 router within the same AS, and two of them will
>> > >> have IBGP
>> > >> > peer with the rest, So I configure these two with the same bgp
>> > >> cluster-id,
>> > >> > and configure the rest to be their route-reflector-clients.
>> Should
>> > I
>> > >> > configure these two to be route-reflector-clients to each
>> > others!!!
>> > >> >
>> > >> > Thanks in advance
>> > >> >
>> > >> > Amin
>> > >> >
>> > >> >
>> > >> >
>> > >>
>> > >>
>> > >
>> _______________________________________________________________________
>> > >
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>> > >>
>> > >>
>> > >>
>> > >>
>> > >
>> _______________________________________________________________________
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>> > >>
>> > >>
>> > >>
>> > >>
>> > >>
>> > > --
>> > >
>> > >
>> > >
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>>
>>
>> --
>> Narbik Kocharians
>> CCSI#30832, CCIE# 12410 (R&S, SP, Security)
>> www.Net-Workbooks.com
>> Sr. Technical Instructor
>>
>>
>> _______________________________________________________________________
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>>
>>
>>
>>
>>
>
-- Narbik Kocharians CCSI#30832, CCIE# 12410 (R&S, SP, Security) www.Net-Workbooks.com Sr. Technical Instructor
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