Re: suppress-map vs advertise-map

When you create an aggregate address using aggregate-address x.x.x.x
m<mask>, then bgp announces aggregate address and all specific networks to
its neighbors.

e,g if you have four swbnets 192.168.0.0/24, 192.168.1.0/24, 192.168.2.0/24and
192.168.3.0/24 and you like to aggregate them, you will use
"aggregate-address 192.168.0.0 255.255.252.0. It will send one aggregate i.e
192.168.0.0/22 plus all the four subnets to its neighbors.
Now you like BGP to advertise aggregate and three subnets and filter
192.168.3.0/24 subnet then you will use suppress map. For suppress map to
filter a route, you will need to create a route-map, match ip prefix or ACL.
Remember, you will need to use permit in prefix/ACL to get the route
suppressed.

Now, advertise-map in the context of aggregation is used to control
aggregation's attributes i.e if an aggregate is used with as-set option,
then aggregate will inherit the attributes of subnets like community,as# .
Now if one AS receives and aggregate with its own AS# in it, it will reject
it, so one of the solutions is to use advertise-map to constitute an
aggregate which has AS#s defined in the route-map.

Also, suppose if one subnet has community no-export, then aggregate will
inherit the same community. you can take that route out from aggregation
list using advertise-map and denying the route whose attribute is set to
no-export. This way aggregate will not inherit the community as well.

On Fri, Jun 26, 2009 at 2:38 AM, Jose Miguel Huertas <
JoseMiguel.huertas_at_telindus.es> wrote:

> Hi Modi,
>
> When you make a supernet with aggregate-address without summary-only
> keyword, you can "suppress" some specific networks using suppress-map, so
> you would announce the supernet and some specific nets.
> For example, we have the bgp networks 10.0.1.0/24, 10.0.2.0/24 and
> 10.0.3.0/24. With aggregate-address we make a supernet 10.0.0.0/22, so we
> would announce this supernet and also the specific nets.
> If we use a suppress-map, we could make not to announce the network
> 10.0.2.0/24, so we would announce the supernet and also 10.0.1.0/24 and
> 10.0.3.0/24
>
> With advertise-map you can make a conditional advertise, let's say, if I
> have this network on my bgp table, then advertise this other network.
>
>
>
>
> -----Mensaje original-----
> De: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] En nombre de
> moditw_at_gmail.co.za
> Enviado el: jueves, 25 de junio de 2009 7:14
> Para: ccielab_at_groupstudy.com
> Asunto: suppress-map vs advertise-map
>
> Hi Group,
>
> I am failing to understand the different between BGP suppress-map and
> advertise-map subcommands. can someone explain to me the different.
>
> Thanks
> Modi
>
>
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Received on Fri Jun 26 2009 - 12:11:55 ART