MPLS

Hello



If an mpls PE router (where customer is connected),
gets two VPN v4 prefixes (the actual "prefix" is same but we have different rds
on top of it ) but they are tagged with same RT ( say on hub , we
created two different vrfs with different Rds and originated default
routes from both vrfs and we peer vpnv4 with MPLS PE router where
customer connects), and on that same mpls PE router (where customer is
connected), we are importing that RT , how does the router decide which
one to import into its vrf?

 

Comments

  • Hi,

    Nice question.

    Consider that at the moment i have nothing to test it but going by logic i would say that the unic piece of information that i could use in order to distinguish the two routes is the RD information. So probably i would install the one with the lowest RD if all the other attributes are equal.

    Probably you could test this faster than me.

     

  • Yes it does seem to install the one with the lower RD but I probably need to test more samples.

     

    Another option was to install both (to do some kind of loadbalancing)Any idea if this can be done?Else we can use this as some GSLB solution :)

     

    I have not really looked at the documentation much.

  • Set MED on a route map and apply it to the default-originate statement and send extended communities in vpnv4

    Hello



    If an mpls PE router (where customer is connected),
    gets two VPN v4 prefixes (the actual "prefix" is same but we have different rds
    on top of it ) but they are tagged with same RT ( say on hub , we
    created two different vrfs with different Rds and originated default
    routes from both vrfs and we peer vpnv4 with MPLS PE router where
    customer connects), and on that same mpls PE router (where customer is
    connected), we are importing that RT , how does the router decide which
    one to import into its vrf?

     



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  • I found the answer. We need to use bgp multipath to install both routes

  • The tricky bit about bgp is to be specific in what you want because there are so many options. Your previous question was about deciding which route to install but now what you say here is if you need both routes installed! These are totally different requirement

    On 24 Apr 2015 18:39, "yogesh" <[email protected]> wrote:

    I found the answer. We need to use bgp multipath to install both routes




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  • peetypeety ✭✭✭

    When the VPNv4 routes arrive via BGP, both are accepted due to the RT that matches the import policy for a particular VRF.

    Both routes come into the VRF, and when the second path arrives, a BGP best path calculation happens. Depending on your code's defaults and any options you've enabled, you may find that the oldest route wins, or you may find that the route with the lowest router ID wins, or you may find that some other criteria wins.

    As you've discovered, BGP multipath will cause multiple paths to be accepted.

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