Re: BGP default route

To add default routes to BGP we can inject them by:

1) using the network command
2) using the redistribute command
3) using the neighbor default-information-originate command

When injecting a 0/0 route into BGP using the network command, a route to
0.0.0.0/0 must already exist in the routing table and the "network 0.0.0.0"
command is required

Injecting a default route through route redistribution requires the
"default-information-orginate" Just as before the default (0/0) route must
already exist in the routing table.

By using the "neighbor 1.1.1.1 default-information-originate" we will not
add a default route to our local table, instead we are advertsing a default
route to our neighbor at 1.1.1.1

With this method the router doesn't care about the existince of a default
route (in other words, the 0/0 route doesn't need to exist in our IP routing
table) You could also setup conditional default routing by using a route-map
too! So as long as a route-map permit clause is matched, the default route
will be advertised to our neighbor at 1.1.1.1

This can be accomplished by using the "route-map check-default" Here is a
sample configuration:

router bgp 111
 neighbor 1.1.1.1 remote-as 111
 neighbor 1.1.1.1 update-source loop 0
 neighbor 1.1.1.1 default-originate route-map check-default
!
ip route 0.0.0.0 0.0.0.0 Null0
!
ip prefix-list def_route seq 5 permit 0.0.0.0/0
!
route-map CHK_DEF permit 10
 match ip address prefix-list def_route

HTH

On Wed, May 4, 2011 at 7:54 PM, emir d souza <emir979_at_gmail.com> wrote:

> Hi Guys,
>
> I'm trying to nail down what is actually required to advertise a default
> route in BGP and in how many ways in can be done?
>
> Any advice anyone?
>
> Cheers!
>
>
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