From: Mohamed M Moustafa (mmma@gawab.com)
Date: Fri Jul 27 2007 - 14:25:23 ART
Hi Herbert,
Just one comment here, next-hop-self has no effect on a RR for its clients,
as next-hop-self changes the next-hop of an eBGP route when sending it to
an iBGP neighbor and thus it is done on routers having eBGP and iBGP in the
case that you don't want to redistribute the next-hop of the eBGP routes
into IGP in order for this route to be valid for the iBGP neighbor.
BR,
Mohammed Mahmoud.
Herbert Maosa <asawilunda@googlemail.com> wrote on 26 Jul 2007, 06:37 PM:
Subject: Re: Usage of Address-family ipv4 unicast ....
>Technically, for any address family configured in BGP you have to activate
>the neighbor. However. the Cisco IOS default is to automatically activate
>neighbors for the IPV4 unicast address-family, so we usually never have to
>consciously put this in the config, and it never shows up in the
>configuration.
>
>
>However, the moment you explicitly activate a bgp neighbor for any of the
>address families ( eg IPV4 multicast ), you will then see the IPV4 Unicast
>address family automatically showing up in the config, to make it apparent
>to you, even though you may not have explicitly put those lines of config.
>
>next-hop-self is usually configured on route-reflectors to the rr-clients,
>or on any BGP speaker if you think the peer does not have an IGP path to
>the
>BGP next hop that may be in the updates that you may be sending that
>neighbor. Remember that BGP has to consider a route valid before
>considering
>it in its decission making process, and part of the validation criteria is
>next hop reachability.
>
>regards,
>
>Herbert.
>
>
>
>On 7/26/07, Sangeetha Nadarajah <ccie1101@gmail.com> wrote:
>>
>> Hi,
>> [1] I have read the cisco doc and it is not very clear when to use
>> the
>> 'address-family ipv4' and 'address-family ipv4 multicast' command ....
>> Can someone explain when to use this and its purpose .....
>>
>> [2] Also, I was doing the technology lab from IE for multicast on
>> 'Multicast BGP' and came to this part of the solution on R4 whereby it
>is
>> connected to R2 by an ethernet segment ....... My question is why is
>> there
>> a next-hop-self to 150.1.24.2 which is the ethernet portion of R2 since
>it
>> is a *directly connected neighbor ? Pls explain as I don't understand
>why
>> the next-hop-self command is needed here ? Most of the time it is used on
>> frame-relay back to back connections only right ?*
>>
>> address-family ipv4 multicast
>> neighbor 150.1.24.2 activate
>> *neighbor 150.1.24.2 next-hop-self
>> *neighbor 150.1.45.5 activate
>> exit address-family
>> !
>> address-family ipv4
>> neighbor 150.1.24.2 activate
>> neighbor 150.1.45.5 activate
>> exit address-family
>>
>> Thank you,
>>
>> Cheers,
>>
>> - sn -
>>
>> _______________________________________________________________________
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>> http://www.groupstudy.com/list/CCIELab.html
>>
>
>
>
>--
>Kindest regards,
>hm
>
>_______________________________________________________________________
>Subscription information may be found at:
>http://www.groupstudy.com/list/CCIELab.html
>
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