Table 1 Feature Information for
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Forwarding functionality consists of the following:
Registration and Tracking: Leaf switch will intercept the ARP and DHCP
packets and learns the IP to MAC binding for the host. In the case of
virtualized environments, VDP may be used to track the VM moves.
End Host Route Distribution
using BGP: MP-BGP is used within the Vinci fabric to distribute the IP
reachability information across the leaf switches in the fabric. Route
reflectors will be used for scalability purposes.
ARP and IPv6 ND
Proxy: One of the goals of Vinci Enhanced forwarding is to eliminate
flooding across the fabric. For this purpose, every leaf switch will act as a
ARP/IPv6 ND proxy for all the hosts connected to the leaf switch.
Gateway: Leaf switches act as the default gateway for routing across
subnets. All the leafs that handle a given subnet are configured with the same
anycast IP address and MAC address.
Behavior at Leaf switches: A fabric VLAN is allocated per tenant VRF in the
Vinci fabric. BGP advertises the reachability of hosts attached to remote leafs
to all the leaf nodes. Ingress leaf switch routes the traffic from the tenant
VLAN to the egress leaf switch where the destination host is attached via the
fabric VLAN. Egress leaf switch routes the traffic back to the tenant VLAN.
This allow the platforms to optimize by scaling the FIB host route table
without scaling the MAC address table.
Routing within the
subnet: Leaf switch responds with the Anycast Default Gateway MAC to the
ARP requests for hosts within the same subnet.
download: Routes are installed by the FIB in hardware based on
conversations to optimize the usage of the FIB entries in the platform. The FIB
entries will also be aged out if the conversation between the hosts ceases to
In the traditional
forwarding with dynamic subnets mode, the functionality for end host
registration and tracking, end host distribution via BGP and Selective FIB
download remains the same as enhanced forwarding. The difference in behavior is
the subnet: ARP requests are flooded in the subnet across the fabric and
traffic within the subnet is bridged. This is predominantly to support "unknown
unicast" cases where the remote host never speaks. In the case of Enhanced
forwarding, IP traffic to unknown destination is dropped.
Anycast Default Gateway:
This solution is still applicable to traffic across subnets. If the host route
for the destination host does not exist, traffic is punted to SUP for glean
processing. In the case of enhanced forwarding, it is expected that the remote
host route is announced via BGP. In the traditional forwarding mode, the glean
process will trigger a ARP request across the fabric for the remote host to
deal with the host that never speaks. While the ARP request will be sent with a
source MAC = Ingress Leaf Router MAC, the ARP payload itself will contain the
IP address = Anycast Default Gateway IP and MAC = Anycast Default Gateway MAC.
Most hosts will respond to the ARP request with a ARP response destined to the
MAC in the ARP payload and in this case, it will be destined to the Anycast
Default Gateway MAC. The egress leaf will receive this ARP response and
announce the remote host via BGP. It is expected that the ARP request in the
ingress leaf switch will eventually timeout.
mentioned in the previous two cases, flooding is allowed in traditional