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scheuri
New Contributor III

BGP propagation and prefix-lists

Hi all

I have three scenarios I need to figure out with prefix lists...and I just need someone to confirm that I am not totally wrong about my approach :)

 

Scenario 1:
I receive about 1'000 prefixes (including the default gateway of 0.0.0.0/0) and I want a route-map as preparation if I need to configure something special down the road.
In order to accept everything from my neighbor I would have used the following prefix-list:

config router prefix-list
    edit "accepteverything"
        config rule
            edit 1
                set prefix any
                unset ge
                unset le
            next
        end
    next
end

Would I be wrong with that?

 

Scenario 2:
Now that I have those 1'000 prefixes including the default gateway of 0.0.0.0/0 I would like to forward everything BUT the default route to another neighbor.
To achieve that I would have used the following prefix-list:

config router prefix-list
    edit "blockrule"
        config rule
            edit 1
                set action deny
                set prefix 0.0.0.0 0.0.0.0
                unset ge
                unset le
            next
            edit 2
                set prefix any
                unset ge
                unset le
            next
        end
    next
end

Would that achieve the goal of forwarding EVERYTHING BUT the default gateaway?

 

Scenario 3:
There is another neighbor I would like to forward nearly everything, but the default route and two other prefixes (192.168.100.0/24 and 192.168.120.0/24).
To achieve that I would have used the following prefix-list:

config router prefix-list
    edit "blockruleextended"
        config rule
            edit 1
                set action deny
                set prefix 0.0.0.0 0.0.0.0
                unset ge
                unset le
            next
            edit 2
                set action deny
                set prefix 192.168.100.0 255.255.255.0
                unset ge
                unset le
            next
            edit 3
                set action deny
                set prefix 192.168.120.0 255.255.255.0
                unset ge
                unset le
            next
            edit 4
                set prefix any
                unset ge
                unset le
            next
        end
    next
end

Would that achieve the goal of forwarding EVERYTHING BUT the default gateaway and said two networks?

 

In general the route-maps used (either route-map-in for scenario 1 or route-map-out for the other two scenaries) would only consist of the respective prefix-list for the moment.

 

Thanks a lot for your help

1 Solution
srajeswaran
Staff
Staff

Duplicate of https://community.fortinet.com/t5/Support-Forum/Question-about-BGP-and-prefix-lists/m-p/264533#M2163...

Prefix list config looks correct.

Regards,

Suraj

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View solution in original post

3 REPLIES 3
srajeswaran
Staff
Staff

Duplicate of https://community.fortinet.com/t5/Support-Forum/Question-about-BGP-and-prefix-lists/m-p/264533#M2163...

Prefix list config looks correct.

Regards,

Suraj

- Have you found a solution? Then give your helper a "Kudos" and mark the solution.

scheuri
New Contributor III

Thank you very much for your reply and I am very sorry for the duplicate.
For some reason I couldn't find the original post and I suspected that I didnt hit "post" after preparing it. Mea culpa!

Toshi_Esumi
Esteemed Contributor III

To find your own posts or replies to other's posts, click your avatar at the top right corner then go to "My profile". In the page, choose the "My Post Activities" tab if it's not pre-selected. Under it, you can find all your Posts and Replies under separate sub-tabs.

 

Toshi

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