Route-maps behavior on following BGP weight attibute

[B@B@r]

dear all ,

i am studying BGP Attributes and following some book

we have two routes in router R1 for going to 2.2.2.0/8 and 22.22.22.0/24 i am studying bgp weight attribute.

by default show ip bgp

Now we want to choose the route for 22.22.22.0/24  as going through 192.168.13.3

for this purpose we choose route-map  as,

                                Config# access-list 1 permit 22.22.22.0 0.0.0.255

my questions are.

1. why we use route-map again with seq no 20,  explain. what is the need of setting weight again 0?

2. is RIB update while pinging the 22.22.22.0/24 or it will execute route-map command before?

3. what if we ignore seq no 20?

my topology

[paul driver]

Hello

---

B@B@r wrote:

1. why we use route-map again with seq no 20,  explain. what is the need of setting weight again 0?

2. is RIB update while pinging the 22.22.22.0/24 or it will execute route-map command before?

3. what if we ignore seq no 20?

Hello

In this case you don't require that routing stanza 20 its only there to capture all other prefixes NOT associated with stanza 10 and it relating access-list  and to make sure all these other prefixes are set to a weight value of 0 (which by default anyway with BGP the default weight of all incoming prefixes is set to 0.)

Now if you wanted to set all the other prefixes to a value other than 0,  then stanza 20 would be most applicable but you would need to increase stanza 10 with higher weight value  so it will take precedence.

As for the rib update, the router would update on its next bgp scan or if you manaully update the rib by a soft clear.

clear ip bgp * soft in|out

I hope that was that clear enough and not to convoluted?

res
Paul