From: Artir Geci (artirgeci@gmail.com)
Date: Tue Mar 08 2005 - 14:31:01 GMT-3
Hi Dillon,
Well, if the bgp route or update is advertised to the internal neighbor
(same AS) and the advertised route is in the same AS, the next-hop would be
the IP address of the router that originated it, but if the advertised route
is from a different AS the next-hop attribute is from the external peer
which the route was learned.
Also with confederations is the same, for example if you put between Rb and
Rc a EBGP confederation link and as global AS u leave AS 2 and you also
leave the same config on Ra, in Ra you still ara going to have the same
results from the network 172.16.0.0 with destination 1.1.1.3 without using
the next-hop-self command.
So it seems to me the same, but if I am wrong or didn't explain it good I am
sure somebody here will correct me :), I tried this on my lab.
I hope it helps you
Artir
-----Original Message-----
From: Dillon Yang [mailto:gzdillon@hotmail.com]
Sent: Tuesday, March 08, 2005 4:52 PM
To: Artir Geci
Cc: Group Study
Subject: Re: Where-next-hop-self
Hi, Artir:
Thanks for your replay.
I just did a lookup on the book. So, in the case, for preventing the
next-hop ip from unreachable, I must choose a iBGP set itself address as
next-hop, right?
Then how about the subas under confederation?
TIA
dillon
----- Original Message -----
From: "Artir Geci" <artirgeci@gmail.com>
To: "'Dillon Yang'" <gzdillon@hotmail.com>; "'Group Study'"
<ccielab@groupstudy.com>
Sent: Tuesday, March 08, 2005 10:45 PM
Subject: RE: Where-next-hop-self
> You have the routers on different AS. If you leave it without changing the
> next-hop (just basic config), at Ra as next-hop for 172.16.0.0 you are
going
> to have 1.1.1.3, so in this case you need to put "neighbor next-hop-self".
>
> If you have Doyle's volume II check there for the next_hop attribute to
> understand why. Or check RFC 1771.
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Dillon Yang
> Sent: Tuesday, March 08, 2005 12:57 PM
> To: Group Study
> Subject: Where-next-hop-self
>
> Hi, all:
>
> A case says the next hop to 172.16.0.0 in Ra should be the 1.1.1.2 in the
> topology:
>
> Ra(spoke)------FR--------Rb(hub)-------FR-------Rc(spoke)
> 1.1.1.1-----------------1.1.1.2-----------------1.1.1.3---172.16.0.0
> As1----------------------As2--------------------As2
>
> It says the next-hop attribute has been carried by Rb to Ra, to prevent
> 1.1.1.3(next-hop) being seen, the command "neighbor 1.1.1.1 next-hop-self"
> must be under "router bgp 2" on Rb. My thought is the 3 routers are in the
> same subnet, so its unnecessary to change the default next-hop. Any
advice?
>
> TIA
> dillon
>
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