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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".


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

3 replies

Userlevel 7
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.
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.
Userlevel 7
Ronie Singh wrote:

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.

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

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