[c-nsp] condition BGP quastion

[Nikolai Abromov]

Hi Bruce, 


First - thanks for your reply I know about bgp condition , but I'm not
quite sure how to setup the rule and there is the problem


 uplink1       uplink2 
     |                | 
[router A] - [router B]
                      |
                 [customer]


and  both uplinks are marked with community strings where first
uplinks is (xxx:001) the second is (xxx:002), I tried to made when the
routes from second
uplink disappear then advertise prefix-list which is in route-map
"advertize" to uplink1
the configuration is something like this


route-map track-as1111, permit, sequence 10
  Match clauses:
    community (community-list filter): 150
  Set clauses:
  Policy routing matches: 0 packets, 0 bytes


route-map advertize, permit, sequence 10
  Match clauses:
    ip address prefix-lists: advertise-this
  Set clauses:
  Policy routing matches: 0 packets, 0 bytes


[..] 
neighbor 192.168.1.1 advertise-map advertize non-exist-map track-as1111

..


so it's that possible or I do something wrong?





On Thu, 27 Jan 2005 10:41:38 -0800, Bruce Pinsky <bep at whack.org> wrote:
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> Nikolay Abromov wrote:
> | Hello List,
> |
> | I have two (bgp) uplink providers which is located on different routers
> | in local segment and i'm wondering is there any method to make backup of
> | my customers with advertise-maps with this topology?
> |
> | scheme:
> |
> | (uplink)             (uplink)
> |      |                     |
> | [router A]  --- [router B]
> |
> |
> 
> Assuming you mean to only advertise your customer's route via router B to
> provider #2 only if the connection via router a to ISP #1 fails, then yes
> you can.  That is called conditional BGP advertisement.  See
> 
> http://www.cisco.com/en/US/tech/tk365/technologies_q_and_a_item09186a00800949e8.shtml#fifteen
> 
> and
> 
> http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a0080094309.shtml
> 
> for more info.
> 
> Of course, the other provider must allow you to advertise the customer's
> route so verify that they have their filters set properly.
> 
> - --
> =========
> bep
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