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Beginner

PI Vlans , EPG and Vxlan Packet Forwarding Issues

Hello all,
  I have few questions that bothers me. I want to be sure about some cases about PI Vlans , EPG communication and VxLAN packet forwarding.  I'm asking my questions in below.

1) In the cisco documentations  it says that at ingress of  leaf switch ,  ACI encapsulates external VLAN, VXLAN, and NVGRE packets in a VXLAN packet. But I know that  if packets destination on the same leaf (local forwarding) , packet isn't encapsulated in VXLan header, as it has no VTEP destination addresses for outer headers.  So, after I read cisco documentations I'm doubt about my knowledge. Even packet's destination on the same leaf, it is still encapsulated with vxlan header?

2) I know that PI(Platform Independent) Vlans map to Encap VLANs and VXLANs.  But if have one epg with multiple VLANS on same leaf, they can communicate because of being in same epg. But when I type "show vlan extended" in leaf switch, I recognized that there are 2 different PI Vlans to map my external VLANs. My questions is that, how these 2 different host communicate with each other if they are in different PI Vlans? If leaf knows can map PI vlans to Bridge Domains, why does it use 2 different PI Vlans instead 1 ? Also if leaf switch only consider EPG to forwarding packets in same layer 2 domain, why it is use PI Vlans?

VLAN Name Encap Ports
---- -------------------------------- ---------------- ------------------------
71 TST:APP_PROFILE1:EPG1 vlan-1669 Eth1/1
73 TST:APP_PROFILE1:EPG1 vlan-1772 Eth1/2

 



Best regards..

 

 

 

1 ACCEPTED SOLUTION

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Participant

Hi OBD

 

1) No, local switched/routed packets are not encapsulated in VXLAN

2) In a BD with multiple EPGs scenario, each EPG will have a unique PI-VLAN pointing to the same BD-VLAN, if you do

show system internal epm vlan 71 and show system internal epm vlan 73, you'll notice that both FD-PI-VLANs point to the same BD-VLAN. Your IDs (71,  73) are the "per EPG PI VLAN", but there is a common "BD PI-VLAN" for both EPGs.

 

HTH

Marcel

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1 REPLY 1
Highlighted
Participant

Hi OBD

 

1) No, local switched/routed packets are not encapsulated in VXLAN

2) In a BD with multiple EPGs scenario, each EPG will have a unique PI-VLAN pointing to the same BD-VLAN, if you do

show system internal epm vlan 71 and show system internal epm vlan 73, you'll notice that both FD-PI-VLANs point to the same BD-VLAN. Your IDs (71,  73) are the "per EPG PI VLAN", but there is a common "BD PI-VLAN" for both EPGs.

 

HTH

Marcel

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