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Default IP interfaces on Fabric nodes

cooperb01
Level 1
Level 1

Hi 

 

After building a new fabric I have noticed the following interfaces are built on each leaf, can you confirm what the purpose of these interfaces?

vlan9, Interface status: protocol-up/link-up/admin-up, iod: 118,
  IP address: 10.0.0.30, IP subnet: 10.0.0.0/27
  IP broadcast address: 255.255.255.255
  IP primary address route-preference: 1, tag: 0
lo0, Interface status: protocol-up/link-up/admin-up, iod: 4,
  IP address: 10.0.176.95, IP subnet: 10.0.176.95/32
  IP broadcast address: 255.255.255.255
  IP primary address route-preference: 1, tag: 0
lo1023, Interface status: protocol-up/link-up/admin-up, iod: 119,
  IP address: 10.0.0.32, IP subnet: 10.0.0.32/32
  IP broadcast address: 255.255.255.255
  IP primary address route-preference: 1, tag: 0

 

I should also mention that these are defined in the overlay-1 vrf.

 

Thanks

Ben

9 Replies 9

dpita
Cisco Employee
Cisco Employee

That's a good question!

 

Lo0 is your loopback referencing the TEP address assigned to the particular switch by the APIC during fabric registration. Specifically this is your physical tunnel endpoint (PTEP) . It is used internally to form tunnels between the leafs for forwarding data plane traffic.

lo1023 is pervasive so it's found on every leaf and it's always the same address  this is a fabric tunnel endpoint or FTEP. Used mostly for AVS when the infra vxlan is extended out of the fabric.

 

The SVI vlanX is the vlan for the infra vlan set during the setup script on the APIC. Issuing a show vlan extended on the leaf can confirm vlan9 in your case translates to the infra vlan. I do not recall at the moment what this address is used for, but I can find out and let you know or one of my peers can beat me to it as well.

 

hope this helps!

 

Thanks for the info.

 

Would the SVI interface be there to allow communication between Leafs and APIC's?

 

Thanks

Ben

Hey Ben,

 

Yes, the infrastructure VLAN is there to allow communication between APICs and switches (both Leafs and Spines). It's so the APIC can distribute policies and perform other administrative functions.

It means that we have to plan our IP scheme to have 3 IPs requires per leaf for infra (e.g. SVI, Lo0 & Lo1023). Please confirm.

 

Regards,

Anser 

Hello

No, in reality you do not need to plan for this. During the setup script you are advised to use a /16 for the infra pool and the APICs will take care of the DHCP allocation from a specific set of pools/subnets created from that /16

Hi dpita, 

I mean to say If I am allocatiing a subnet and If I am planning for 100 leafs + 3 APICs. It means my infra will use 3 IPs per leaf + 3 IPs for 3 APICs or each leaf will use 2 IPs (SVI & VTEP) and FTEP IP will remain same through out the fabric (in each leaf).

The only unique address would be the lo0 which is the leafs TEP address assigned by the APIC during fabric registration. the vlanX SVI and the lo1023 are usually shared among all leafs. 

 

Hi dpita,

 

When we extend the AVS out of the fabric over the layer 2 network, VTEP of AVS will communicate with FTEB of the fabric (leaf). Is this the purpose of FTEB lo1023? Please confirm.

 
Regards,

Anser

Hello,

Yes that is correct.

On the other hand, the tunnel built between the leafs and the AVS to forward traffic will reference their standard TEP addresses. 

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