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    NX-OS question... Loopback interface down/down?!

    Micheline

      Howdy all and a happy Monday--I'm in the process of configuring VXLAN.  I have one spine connected to two leaf switches.  I'm using OSPF as the L3 underlay IGP.  I'm all humming along thinking everything is good... except that my VXLAN fabric doesn't come up and my VTEPs (the two leaves) don't peer.  So I go back to troubleshoot the fabric, and I go all the way back to pre-requisites for VXLAN.  Namely, IP connectivity between VTEPs. (I swear I checked this before....)  So I tshoot some more and find that OSPF is not advertising the route for either VTEP IP.  Digging more, I get this weirdness:

       

      pod4-spine-1(config-if)# sipib

      IP Interface Status for VRF "default"(1)

      Interface            IP Address      Interface Status

      Lo0                  4.4.0.1         protocol-up/link-up/admin-up      

      Lo1                  10.0.0.100      protocol-up/link-up/admin-up      

      Po401                172.20.0.58     protocol-up/link-up/admin-up      

      Po402                172.20.0.62     protocol-up/link-up/admin-up      

      Po4001               172.24.0.1      protocol-up/link-up/admin-up      

      Po4002               172.24.0.5      protocol-up/link-up/admin-up

       

      pod4-leaf-1(config)# sipib

      IP Interface Status for VRF "default"(1)

      Interface            IP Address      Interface Status

      Vlan10               10.10.0.1       protocol-up/link-up/admin-up      

      Lo0                  4.4.1.1         protocol-down/link-down/admin-up  

      Po4001               172.24.0.2      protocol-up/link-up/admin-up      

      Eth1/46              172.24.0.13     protocol-down/link-down/admin-down

       

      pod4-leaf-2(config)# sipib

      IP Interface Status for VRF "default"(1)

      Interface            IP Address      Interface Status

      Vlan10               10.10.0.2       protocol-up/link-up/admin-up      

      Lo0                  4.4.1.2         protocol-down/link-down/admin-up  

      Po4002               172.24.0.6      protocol-up/link-up/admin-up      

      Eth1/46              172.24.0.14     protocol-down/link-down/admin-down

       

       

      That is, Lo0 on Leaf1 and Leaf 2 is down/down.  In contrast, the route to the up/up interface is being advertised.  I've never seen a loopback interface down, except when it's been shut, and these are clearly not shut  (admin-up...just for good measure, I shut/no shut each Lo0.  You can see on the leaf switches, e1/46 IS shutdown for comparison.)    Here's the config for Lo0--Leaf 1, Leaf2, and Spine 1:

       

      pod4-leaf-1(config)# srint lo0

       

      !Command: show running-config interface loopback0

      !Time: Mon Jul 31 17:04:52 2017

       

      version 7.0(3)I4(2)

       

      interface loopback0

        description Leaf1 Router ID

        ip address 4.4.1.1/32

        ip ospf network point-to-point

        ip router ospf POD4 area 0.0.0.0

        ip pim sparse-mode

       

      pod4-leaf-2(config-if)# srint lo0

       

      !Command: show running-config interface loopback0

      !Time: Mon Jul 31 17:05:08 2017

       

      version 7.0(3)I4(2)

       

      interface loopback0

        description Leaf2 Router ID

        ip address 4.4.1.2/32

        ip ospf network point-to-point

        ip router ospf POD4 area 0.0.0.0

        ip pim sparse-mode

       

      Here's the config for the spine's Lo0:

       

      pod4-spine-1(config-if)# srint lo0

       

      !Command: show running-config interface loopback0

      !Time: Mon Jul 31 17:06:18 2017

       

      version 7.0(3)I4(2)

       

      interface loopback0

        description Spine1 Router ID

        ip address 4.4.0.1/32

        ip ospf network point-to-point

        ip router ospf POD4 area 0.0.0.0

        ip pim sparse-mode

       

      The spine is a Nexus 9332PQ, and the leaves are both Nexus 9372PX.  I am just stumped at this point.  And I've gone cross-eyed comparing the config between the loopback that works and the loopbacks that don't work.  Any suggestions for other tshooting would be very welcome! 

       

      Thanks in advance!  MM

         
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