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TOPIC: BGP Route Advertisement Question

BGP Route Advertisement Question 9 years 10 months ago #31362

I'm sorry if this is kind of long. I'm sure there's a simple answer. Hoping someone can shed some light:

Let’s say the “major” network for my site is /16

Let’s say I had an interface that I sub’d out into 3 vlans. (gig1/0 sub’d into g1/0.10, g1/0.20 & g1/0.30)
Networks are
vlan 10 = /24
vlan 20 = /24
vlan 30 = /24

I have 2 different bgp peers I want to advertise networks to.
One peer I want to advertise the whole /16. The other peer I only want to advertise /24.

Regarding the peer that I wanted to advertise /16, I noticed that I couldn’t just put "network mask" under my “router bgp” section of the config. I didn’t have any loopback interfaces with any /16 IP’s assigned to them. Nor did I have “redistribute connected” within my “router bgp” section of the config.

So I generated the router by adding a static route to Null 0. (ip route null 0) then I added the command “redistribute static” under the “router bgp” portion of the config. By doing this, I was able to generate the /16 route. (NOTE, I haven’t or didn’t need to add the “network mask” statement under the “router bgp portion of my config.)

So now I am sending my /16 route to the peer accepting my /16 advertisement.

I want to send ONLY the /24 to my other peer.
I was able to do this by simply adding the statement “redistribute connected” under the “router bgp” portion of my config. (Easy enough) BUT my question is… there a way to advertise my /24 to the peer who wants to see it, without using the “redistribute connected” command?

And secondly, if I were to add the network statement under my “router bgp” for the /16, could I also add the /24 network statement under router bgp? (And removing the redistribute connected statement.)

Is there a way to advertise routes to different BGP peers without using redistribute static and/or redistribute connected?

So it would look like

Router bgp 65425
network mask
network mask

Your input is greatly appreciated

Re: BGP Route Advertisement Question 9 years 10 months ago #31369

There needs to be an exact match in the routing table when using the network command. network mask should work for you since it is tied to a connected interface (VLAN 30). network will not work but you could add an aggregate statement to do this.

Below Neighbor is the one that should not recieve the summary route, neighbor will receive the summary.

router bgp 44
no synchronization
bgp log-neighbor-changes
network mask
neighbor remote-as 100
neighbor remote-as 901
neighbor route-map BGP out

ip prefix-list BGP seq 5 permit

! Deny the aggregate route. This is tied in neighbor statement.
route-map BGP deny 10
match ip address prefix-list BGP
route-map BGP permit 100

! Route map 100 is needed. An empty route-map has implict match everything.

Re: BGP Route Advertisement Question 9 years 10 months ago #31370

Thank you Perlhack. I will try this in the lab.

You rock!

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