Re: prefix advertisement in bpg

yes.. i should have worded it much better :) please check my previous
message,plus David's msg too.

On Mon, Apr 15, 2013 at 2:29 PM, Imran Ali <immrccie_at_gmail.com> wrote:

> Ahmed ,
>
> Synchronisaiton is legacy rule and is off by default , so you dont need
> any route in IGP to adveritse a bgp route.
>
>
>
>
> On Mon, Apr 15, 2013 at 12:20 PM, Ahmed Hussain <engine10_at_gmail.com>wrote:
>
>> David's right, not necessarily IGP, but the prefix has to be in your
>> routing table before BGP can advertise it to its neighbors. Simply put u
>> are advertising a /16 to ur neighbours but that /16 may not be on in ur
>> routing table. So u use the null0 static route, sometimes also called a
>> "pull route." This has nothing to do with NAT.
>>
>>
>> On Mon, Apr 15, 2013 at 12:42 PM, David Rothera <david.rothera_at_gmail.com>wrote:
>>
>>> No, it will be using a null route so that it can advertise a summary
>>> route such as the /16 in your example.
>>>
>>> The null route is used so that when a packet arrives it checks to see if
>>> there is a route matching the destination that is more specific than the
>>> /16 null route, if there isn't then the null route is used and the traffic
>>> is dropped.
>>>
>>>
>>> Regards
>>>
>>> David Rothera
>>> CCIE #38338
>>> Sent from my iPhone
>>> Please excuse any mistakes and brevity.
>>>
>>> On 15 Apr 2013, at 08:16, Imran Ali <immrccie_at_gmail.com> wrote:
>>>
>>> so far i did not see any logical reason to point it to null 0 ,
>>>
>>> in case servers are using private ip, and they do nat to translate
>>> public block to private block . but since this public subnet is non
>>> existant we need a route for nat to work,
>>>
>>> is my mind correct ?
>>>
>>>
>>> On Mon, Apr 15, 2013 at 9:40 AM, David Rothera <david.rothera_at_gmail.com>wrote:
>>>
>>>> It doesn't have to be in an IGP (unless you are using IGP sync) but
>>>> simply the routing table itself, either by a static route or from an IGP.
>>>>
>>>> Regards
>>>>
>>>> David Rothera
>>>> CCIE #38338
>>>> Sent from my iPhone
>>>> Please excuse any mistakes and brevity.
>>>>
>>>> On 15 Apr 2013, at 06:14, Ahmed Hussain <engine10_at_gmail.com> wrote:
>>>>
>>>> > Before BGP can advertise the prefix it has to be in IGP. thats what
>>>> the
>>>> > null route is doing.
>>>> >
>>>> >
>>>> > On Fri, Apr 12, 2013 at 10:01 PM, Imran Ali <immrccie_at_gmail.com>
>>>> wrote:
>>>> >
>>>> >> why some bgp implementations adds a null route for advertised
>>>> prefixes
>>>> >>
>>>> >> ex
>>>> >>
>>>> >> router bgp 2
>>>> >> bgp log-neighbor-changes
>>>> >> network 128.16.16.0 mask 255.255.255.0
>>>> >> network 130.130.0.0
>>>> >> neighbor 10.10.10.1 remote-as 1 * neighbor 10.10.10.1 advertise-map
>>>> >> ADVERTISE non-exist-map NON-EXIST***neighbor 10.10.20.3 remote-as 3
>>>> >> !
>>>> >> ip route 130.130.0.0 255.255.0.0 *Null0*
>>>> >>
>>>> >>
>>>> >>
>>>> >> is has something to do with NAT ?
>>>> >>
>>>> >>
>>>> >> Blogs and organic groups at http://www.ccie.net
>>>> >>
>>>> >>
>>>> _______________________________________________________________________
>>>> >> Subscription information may be found at:
>>>> >> http://www.groupstudy.com/list/CCIELab.html
>>>> >
>>>> >
>>>> > Blogs and organic groups at http://www.ccie.net
>>>> >
>>>> >
>>>> _______________________________________________________________________
>>>> > Subscription information may be found at:
>>>> > http://www.groupstudy.com/list/CCIELab.html

Blogs and organic groups at http://www.ccie.net
Received on Mon Apr 15 2013 - 14:51:55 ART