Packet Flow in FabricPath
In order to send traffic in fabric path domain, Once Network administrator has configured the Fabric Path correctly, Switch table and other table like Multi destination tree will already be created.
In previous section we have given idea about how switch table will be created now we will learn how Multidestination tree along with MAC table will be populated and then how data traffic will flow between source and destination.
Following are the table types which will be used for following types of table.
- For Broadcast, unknown unicast, and Multicast: Multidestination tree, MAC table is used.
- For Unicast traffic (data traffic): Switch table and MAC Table is used.
Now we will see how multidestination tree is created to handle broadcast, unknown unicast, and Multicast traffic.
For broadcast (ARP Request), unknown unicast (ARP Reply in fabric path only), and multicast, multidestination trees are created. In fabric path domain two multidestination trees are created for which two root switch to be defined. Root Switch can be define or elected by following method.
- Root Priority: 8 bit value between 0 and 255 (default value is 64)
- System ID: 48 bit composed of VDC MAC address
- Switch ID: 12 Bit unique SID.
In this domain, one switch become root for multidestination Tree 1 by using values. Higher values will be used for Root Switch Negotiation. Once a switch becomes root for Multidestination Tree 1 then second root switch will be negotiated by using these values among other switches. So by this we have two root switch one root switch for Multidestination Tree 1 and second root switch for Multidestination Tree 2.
By root-Priority command you can also define manual Priority of any switch.
Once Root Switch is defined, Root Switches will create multidestination Tree (Tree-1 and Tree-2) based on shortest path to reach to all other switches in fabric path domain.
Below diagram can explain what we have read above:
Out of above switch two root Switches S100 for Tree-1 and S400 for Tree-2 is defined. Now S100 and S400 will create its respective Multidestination based on shortest path to reach other switches.
Before Going to How data traffic flows and how ARP request and ARP reply works, Lets understand how MAC address learning occurs in Fabric Path domain.