Re: MSDP

Hey Splinter and team,

Been a couple of years since I have worked SP stuff ... hope I got all this
right.

The challenge for the IP address you use is simple end to end connectivity.
Since BGP peers are going to be reachable, it is a good idea to use this
same address.

What happens if you use loopbacks or alternate addresses? What about
configuring this in an inter-as relationship with other SPs involved ... ?
The configs get a bit more complicated and then you have to share / leak
more routing info between the various AS / SPs than you want to. This is
why Inter-AS MVPN is such a challenge for the real world. The MSDP path is
one that is from one end to the other end ...

For SPs, to keep it clean, use the same address that BGP uses. For more
'fun', use an additional or loop address and make sure it is reachable from
end to end.

Last note to make ... you do not have to use BGP, but who would run an IGP
between SPs / Inter-AS? No one ... people are going to run BGP between AS,
and not IGP ... so using the BGP address makes more sense from an
implementation perspective. Kind of figures though that the CCIE lab might
make this more 'fun' for you. Certainly tracing this from end to end would
be more of a challenge ...

HTH Splinter and have a good night,

Andrew Lee Lissitz

On Tue, Jun 9, 2009 at 7:29 AM, Splinter <splinter330_at_gmail.com> wrote:

> I can set ip up both ways and it works cause there is reachability.
>
> So if ebgp peer is set to peer with your interface and yoiu set up your
> msdp
> to peer using loopback addresses, then from what is stated below would mean
> that I have done my config incorrectly.
>
> This is why is asked, it is in the DOC CD.
>
> Take from:
>
> http://www.cisco.com/en/US/docs/ios/12_1/iproute/command/reference/1rdmsdp.html#wp1017727
>
> ip msdp peer Usage Guidelines
>
> If you are also BGP peering with this MSDP peer, you should use the same IP
> address for MSDP as you do for BGP. However, you are not required to run
> BGP
> or MBGP with the MSDP peer, as long as there is a BGP or MBGP path between
> the MSDP peers. If there is not, you must configure the *ip msdp
> default-peer* command.
> Examples
>
> The following example configures the router at the IP address 131.108.1.2
> as
> an MSDP peer to the local router. The neighbor belongs to autonomous system
> 109.
>
> ip msdp peer 131.108.1.2 connect-source ethernet 0
>
> router bgp 110
>
> network 131.108.0.0
>
> neighbor 131.108.1.2 remote-as 109
>
> neighbor 131.108.1.2 update-source ethernet 0
>
>
>
> On Tue, Jun 9, 2009 at 1:20 PM, Abdul <rslab007_at_gmail.com> wrote:
>
> > Msdp is not related to BGP at all. It's used for PIM RP redundancy. So
> yes,
> > provided you set a peer IP address that is reachable by routing table on
> > both sides, your msdp peer relationship will be established.
> >
> >
> > On Jun 9, 2009, at 7:04 AM, Splinter <splinter330_at_gmail.com> wrote:
> >
> > Hi GS,
> >>
> >> when configuring MSDP do you have to have you MSDP peer same as your
> ebgp
> >> neighbour?
> >>
> >> EG:
> >>
> >> Router bgp 10
> >> nei 172.10.10.4 remote-as 11
> >>
> >> ip msdp peer 172.10.10.4
> >>
> >>
> >> Router bgp 11
> >> nei 172.10.10.3 remote-as 10
> >>
> >> ip msdp peer 172.10.10.3
> >>
> >> or can the msdp peer be set up using the EBGP loopback addresses?
> >>
> >> my msdp peer is up even thou my msdp peer address is different from the
> >> bgp
> >> neighbour.
> >>
> >> Please clarify
> >>
> >> Splinter
> >>
> >>
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-- 
Andrew Lee Lissitz
all.from.nj_at_gmail.com
Blogs and organic groups at http://www.ccie.net