Mpls implicit null

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  • Updated 2 years ago
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Hello everyone,

I've been trying the mpls under Extreme x460 on my lab, but after the mpls establihed
neighbourhood the switch is able to announce labels, but when it received label from other router(cisco, mikrotik) it is re-label as impnull.

I've tried to do a lot of thing in others routers and itself, i unconfigured the  switch and reconfigured again, and the same thing.

Follow the result from output command sh mpls label

Advertised     Destination  Label     Peer  NHop
Label              Mapping  Flags    Label  Type  NextHop            Name
-------------------------------------------------------------------------------
0x00434  172.16.254.255/32    -LE       --  vlan  loopback01         --           
0x00436     12.12.12.12/32    -LT  ImpNull    IP  10.10.1.2          --           
0x00435    172.16.2.255/32    -LT  ImpNull    IP  172.16.254.2       --           

Received       Destination  Label     
Label              Mapping  Flags   NextHop            Name
------------------------------------------------------------------------------
ImpNull     12.12.12.12/32    -LT   10.10.1.2          --           
ImpNull    172.16.2.255/32    -LT   172.16.254.2       --    

I don't know why this switch is putting in this label received as impNull, and it is taking my vpls to down.

my config about mpls.

#
# Module mpls configuration.
#
configure mpls add vlan "Lab_mk01"
enable mpls vlan "Lab_mk01"
enable mpls ldp vlan "Lab_mk01"
configure mpls add vlan "loopback01"
enable mpls vlan "loopback01"
enable mpls ldp vlan "loopback01"
configure mpls add vlan "ngm"
enable mpls vlan "ngm"
enable mpls ldp vlan "ngm"
configure mpls lsr-id 172.16.254.255
enable mpls protocol ldp
enable mpls


Image   : ExtremeXOS version 15.7.2.9 v1572b9 by release-manager
          on Wed Jul 8 16:27:07 EDT 2015


Tks
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welisson

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Posted 2 years ago

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Grosjean, Stephane, Employee

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Hi,

Is the egress MPLS router the Cisco? If it advertises an Implicit NULL label (3), then the Penultimate MPLS router has to pop the label. That's PHP. I believe this is a default for Cisco. Try that on the Cisco (if this is lab, not production):

mpls ldp explicit-null
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welisson

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Hi Grosjean,

So, in this case the cisco and mikrotik is working as an LER and the Extreme as LSR, but the extreme has been worked as an ler as well, so that the vpls wasn't able to up, and because it took me to put a cisco in scene to try and take off all possibility that could there is.

let me show my scene 1
computer<----->extreme(LER)<------>mikrotik1<--->mk2(LER)<---->Laptop
 in this scene i can see label being generated and exchanged between mikrotiks and extreme, but when the extreme received the label it put an impnull, thinking about php i've tried to use just mikrotik 1 and mk2 as ler/lsr and worked fine and  took vpls  up, but if i trought the vpls over extreme is not working anymore, i don't know why.

the other scene is
cisco(LER)<---->extreme<--->mikrotik1<-->mk2(LER)<---->laptop
so the extreme put implicitly this label as impnull when they come from mikrotik1 and come from cisco.

Ok, may be the php, but why is it put imp null in packets come from mikrotik1?