VLAN Encapsulation in ACI – Deep Dive
There are two types of VLANs used in ACI
- External VLAN: Used for External Communication and Integration
- Internal VLAN: It is also called as Platform Independent Vlan whose scope is local to each leaf. ACI has no control how Platform VLAN is allocated to traffic going via leaf. APIC allocates PI VLAN per EPG, Per BD and these allocation is local to leaf and is different to each Leaf.
Cisco ACI fabric internally does not use VLANs as traditional switches but it translates externally connected VLANs to Flooding Domain, Bridge Domain and VXLANs. All of this is happening at the ingress to the fabric.
Here we can see the ACI has allocated the Platform VLAN to each VLAN which its receives from ingress port. Example from port Eth1/11, Traffic comes to Leaf with encapsulation of Ethernet vlan 1675 and upon receive, it allocates VLAN 12 randomly on that leaf switch.
show vlan extended output command you can see how internal VLANs are encapsulated to VXLANs or external VLANs. With this command, you can easily see which external VLANs are used on the particular leaf switch.
There are various Internal Platform VLAN used by ACI on each Leaf and they are independent to each other. Several VLANs exist on a leaf switch. There are two commands most commonly used for troubleshooting purposes: show vlan extended and show system internal eltmc info vlan brief. In the output of the later command you can see a table with several different VLANs:
Different Platform VLANs used in ACI are:
VlanId: is the PI (platform independent) VLAN of the system and is locally significant to each switch. This is the same VLAN as seen in the output of the command show vlan.
Hw_VlanId: is the VLAN used in ASICs but is usually not relevant for a user.
BD-VLAN: is used to represent a bridge domain and can link multiple FD-VLANs (encap VLANs) together with multiple hardware VLANs and internal VLANs. It is one forwarding aspect used by the Broadcom ASIC to determine if traffic should be locally switched or forwarded to the Northstar ASIC for processing. The BD-VLAN connects different local FD-VLANs to a single bridge domain, and is used on the Broadcom ASIC to determine the Layer 2 broadcast domain. If for example two different access_enc VLANs have the same BDVlan ID it means they belong to two EPGs that are part of the same BD.
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FAQs
Internal VLAN: It is also called as Platform Independent Vlan whose scope is local to each leaf. ACI has no control how Platform VLAN is allocated to traffic going via leaf. APIC allocates PI VLAN per EPG, Per BD and these allocation is local to leaf and is different to each Leaf.
What is VLAN encapsulation? ›
In order that a network device can identify frames of different VLANs, a VLAN tag field is inserted into the data link layer encapsulation. The format of VLAN-tagged frames is defined in IEEE 802.1Q issued in 1999.
What are the two types of encapsulation used to carry data from multiple VLANs over trunk links? ›
There are two trunking protocols: 802.1Q: This is the most common trunking protocol. It's a standard and supported by many vendors. ISL: This is the Cisco trunking protocol.
How does VLAN work in Cisco ACI? ›
VLAN in Cisco ACI is just an identifier to classify endpoints to each EPG. Bridge domain is the layer 2 domain instead of VLAN. There are 4 types of identifiers in Cisco ACI: Access Encapsulation VLAN ID: we can call it VLAN on the wire which is used to communicate with external device.
What is external or on the wire encapsulation? ›
External or On the wire encapsulation is used for allocating VLANS for each EPG associated to the VMM domain. The VLANs are used when packets are sent to or from Leaf switches.
What is the purpose of encapsulation in networking? ›
Encapsulation and deencapsulation allow the design of modular communication protocols so to logically separate the function of each communications layer, and abstract the structure of the communicated information over the other communications layers.
What are the 3 types of VLANs? ›
- Data VLAN - A data VLAN is used to separate and prioritize data traffic within a network.
- Voice VLAN - A voice VLAN is designed to handle voice over IP (VoIP) traffic, which includes voice calls and other real-time communication services.
- Static VLAN - Common type of VLAN, manually assign switch ports.
Types of encapsulation in OOP
Object-oriented programming has three ways to implement encapsulation: member variable, function, and class.
What is IEEE 802.1Q encapsulation? ›
802.1Q is the networking standard that defines virtual LANs (VLANs) on an Ethernet network. VLANs are logical networks that share a single physical connection using 802.1Q tagged frames. An Ethernet frame can contain an 802.1Q tag, with fields that specify VLAN membership and user priority.
What is encapsulation in Cisco? ›
Data Encapsulation. When a host transmits data across a network to another device, the data goes through encapsulation: It is wrapped with protocol information at each layer of the OSI model. Each layer communicates only with its peer layer on the receiving device.
There are two types of VLANs used in ACI. External VLAN: Used for External Communication and Integration. Internal VLAN: It is also called as Platform Independent Vlan whose scope is local to each leaf. ACI has no control how Platform VLAN is allocated to traffic going via leaf.
What are the three main components of Cisco ACI? ›
ACI consists of three key components: the Application Policy Infrastructure Controller (APIC), the leaf switches, and the spine switches. The APIC is a centralized controller that manages all aspects of the ACI fabric.
How does Vxlan work in ACI? ›
In ACI, VXLAN solves this dilemma by decoupling Layer 2 domains from the underlying Layer 3 network infrastructure. As traffuc enters the fabric, ACI encapsulates and applies policy to it, forwards it as needed across the fabric through a spine switch (maximum two-hops), and de-encapsulates it upon exiting the fabric.
What is the process of encapsulation? ›
Encapsulation can be defined as a process where a continuous thin coating is formed around solid particles, liquid droplets, or gas cells that are fully contained within the capsule wall (King, 1995).
What is the encapsulation protocol? ›
Encapsulation protocols connect the layer- 2 (link layer) protocol with the layer-3 (network layer) protocol. For an ASE to analyze network-layer protocols, it must know how to access them above the link layer. Toward this end, you can set the ASE's encapsulation protocol.
What is the meaning of de-encapsulation? ›
Decapsulation, also known as unwrapping or de-encapsulation, is a process in network protocols where a device, such as a router or a switch, removes headers or trailers from a data packet to reveal the actual data payload.
What is encapsulation in routing? ›
Encapsulation adds information to a packet as it travels to its destination. Decapsulation reverses the process by removing the info, so a destination device can read the original data.
How does Vxlan encapsulation work? ›
VXLAN tunneling protocol encapsulates Layer 2 Ethernet frames in Layer 3 UDP packets. This encapsulation enables you to create virtual Layer 2 subnets or segments that can span physical Layer 3 networks. In a VXLAN overlay network, a VXLAN network identifier (VNI) uniquely identifies each Layer 2 subnet or segment.
What is the purpose of Dot1q? ›
Definition and Purpose
Dot1q VLAN tagging allows network administrators to divide a LAN into multiple VLANs and manage them efficiently. Each VLAN is assigned a unique VLAN ID that enables switches to separate VLAN traffic from other VLANs.
