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On a L3 switch there are two equal cost ISIS routes.

Destination/Mask Proto Pre Cost Flags NextHop Interface

10.150.4.12/32  ISIS-L2 15   10          D   10.200.15.42    Vlanif27
                ISIS-L2 15   10          D   10.200.15.38    Vlanif26

the switch is huawei s5700 I want to understand which route will be taken and why?

also if MPLS is enabled on it. I see there are two LSP's as shown in the image.

enter image description here and MPLS RFC says: "Packets belonging to an FEC will always follow the same path".

so I want to understand which LSP will be chosen and why? is there any kind of load balancing happening?

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  • I don't know for the exact device and firmware you are using but in general, when two equal cost IP paths are available you will load balance over them both, it's call Equal Cost Multi-Path Routing. That is fairly standard across all hardware vendors. If you are running MPLS here too (without Traffic Engineering) you may well load-balance here still but that is depending on your hardware/software vendor so you need to check their documents to confirm.
    – jwbensley
    Jan 7, 2015 at 16:13
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin ♦
    Aug 11, 2017 at 2:28

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You should check FIB on your switch if you find there two records it means that the switch will load-balance. The command is: display fib x.x.x.x 32 verbose In the output you'll also see whether switch will use mpls switching for this FEC and what LSP will it pick. Fields LspFwdFlag and LspToken indicate this.

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