Appreciate if someone can explain clearly the use case of command "enable ospf mpls-next-hop " & "enable iproute mpls-next-hop".

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Appreciate if someone can explain clearly the use case of command "enable ospf mpls-next-hop " & "enable iproute mpls-next-hop".

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Ronie Singh

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Posted 2 months ago

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Grosjean, Stephane, Employee

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Hi,


you'll typically use "enable iproute mpls-next-hop" for L3VPN, imho.

This command will tell the router to prefer the MPLS LSPs rather than the IGP routes for entries that are learnt by both.

Here's an example:

PE2.28 # sh iproute
[...]
mp 192.168.255.40/32 15.0.210.1 1 U--D---um-L-- vl210 0d:4h:39m:53s
#oa 192.168.255.40/32 15.0.210.1 22 UG-D---um---- vl210 0d:4h:41m:51s

PE2.29 # enable iproute mpls-next-hop
PE2.30 # show iproute
[...]
#mp 192.168.255.40/32 15.0.210.1 1 U--D---um-L-- vl210 0d:5h:3m:30s
oa 192.168.255.40/32 15.0.210.1 22 UG-D---um---- vl210 0d:5h:5m:28s


The other command, "enable ospf mpls-next-hop" is to tell ospf to use an MPLS LSP to reach the destination, when available.
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Ronie Singh

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Hi Grosjean,

Thank you for your explanation and really appreciate it.  As per following snippet, can I confirm the path to PE2 is preferring via OSPF even though there is mpls ldp for the same destination ?

Does it mean the forwarding will be via pure L3 instead of labeling ?

PE1 # show iproute 172.17.80.55/32
Ori  Destination        Gateway         Mtr  Flags         VLAN       Duration
 mp  172.17.80.55/32    172.17.70.125   1    U--D---um-L-- PE2-Via-P1 2d:18h:36m:2s
#or  172.17.80.55/32    172.17.70.125   16   UG-D---um--f- PE2-Via_P1 2d:18h:36m:2s

Thanks.


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Grosjean, Stephane, Employee

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in your example, the "#" is important, this is the entry in the FIB. Here, it's using pure L3.