Lightweight host multihoming
Described herein are systems and methods for host multihoming with no state synchronization between top-of-rack (ToR) switches coupled to multiple hosts. ToR switches of a multi-homing system share a virtual MAC address and respond to Address Resolution Protocol (ARP) requests and/or Neighbor Discovery (ND) solicitations for a default gateway IP address from the host with the virtual MAC address. Ports on a ToR switch may be configured either with a static ARP and/or ND entry, or be configured to learn via a discovery protocol. The lightweight host multihoming system may have modified flooding behavior, ARP/ND handling, and data path forwarding. ARP/ND traffic from a host is processed by a ToR switch, while other multicast traffic may be discarded. Embodiments of the host multihoming system provide a lightweight solution for software implementation with minimal changes imposed on the host or network design.
1. A method for host multi-homing comprising:
for a network switch in a multi-homing system performing steps comprising:
configuring the network switch with a virtual MAC address that is the same as another network switch in the multi-homing system;
configuring the network switch with a virtual Internet Protocol (IP) address that is the same as the another network switch, the virtual IP address is used as a default gateway for the multi-homed system;
for a host that is to be multi-homed or for a host that is singled-homed but in a same subnet as a multi-homed host, configuring one or more ports on the network switch that are connected to the host with:
at least one of a static Address Resolution Protocol (ARP) entry and Neighbor Discovery (ND) entry; or
a discovery protocol-based registration, responsive to a discovery protocol is used in one port, the port is disabled for user traffic until an IP address to MAC address binding is received from the host by the discovery protocol, the network switch and the another network switch have no state synchronization regarding the MAC address;
upon the one or more ports coming up, advertising via a routing protocol a host route for the host; and
processing ARP or ND traffic from the host.
2. The method of claim 1 further comprising:
discarding any non-ARP, non-ND broadcast, unknown unicast and multicast (BUM) traffic from the host.
3. The method of claim 1 further comprising:
forwarding traffic within a subnet using the virtual MAC address.
4. The method of claim 1 further comprising:
using a Link Aggregation Control Protocol (LACP) or Bidirectional Forwarding Detection (BFD) to determine liveness of a port of the host.
5. The method of claim 4 wherein the BFD is a micro-BFD protocol.
6. The method of claim 4 further comprising:
responsive to liveness of the port of the host being lost, withdrawing via the routing protocol the host route for the host.
7. The method of claim 1 wherein the network switch and the another network switch are top-of-rack (ToR) switches.
8. The method of claim 1 wherein the discovery protocol is a Link Layer Discovery Protocol (LLDP).
9. The method of claim 1 wherein the discovery protocol is a Virtual Station Interface (VSI) Discovery and Configuration Protocol (VDP).
10. A multi-homing system comprising:
one or more hosts; and
a pair of network switches coupled to the one or more hosts, the pair of network switches have a shared virtual MAC address and a shared virtual Internet Protocol (IP) address, the shared virtual IP address is used as a default gateway for the multi-homed system, each network switch is configured to:
either configure an Address Resolution Protocol (ARP) or Neighbor Discovery (ND) entry, or receive, via a discovery protocol-based registration, an IP address to MAC address binding of a host attached to one or more ports, the host is to be multi-homed or singled-homed but in a same subnet as a multi-homed host, the network switch and another network switch of the pair of network switches have no state synchronization regarding the MAC address, the one or more ports are disabled for user traffic until the IP address to MAC address binding is received from the host by the discovery protocol;
advertise via a routing protocol a host route for the host upon the one or more ports coming up; and
process ARP or ND traffic from the host.
11. The multi-homing system of claim 10 wherein the pair of network switches are top-of-rack (ToR) switches.
12. The multi-homing system of claim 11 wherein each ToR switch discards broadcast, unknown unicast and multicast (BUM) traffic from the host.
13. The multi-homing system of claim 11 wherein each ToR switch forwards traffic within a subnet using the shared virtual MAC address.
14. The multi-homing system of claim 11 wherein each ToR switch uses a Link Aggregation Control Protocol (LACP) or Bidirectional Forwarding Detection (BFD) to determine liveness of a port of the host.
15. The multi-homing system of claim 14 wherein the BFD is a micro-BFD.
16. A non-transitory computer-readable medium or media comprising one or more sequences of instructions which, when executed by one or more processors, causes the steps for host multi-homing in a multi-homing system comprising one or most hosts to be performed comprising:
configuring a network switch in the multi-homing system with a virtual MAC address that is the same as another network switch in the multi-homing system;
configuring the network switch with a virtual Internet Protocol (IP) address that is the same as the another network switch, the virtual IP address is used as a default gateway for the multi-homed system;
configuring either a static Address Resolution Protocol (ARP) or Neighbor Discovery (ND) entry, or configuring a discovery protocol-based registration for one or more ports on the network switch that are connected to a host that is to be multi-homed or a host that is singled-homed but in a same subnet as a multi-homed host, the one or more ports are disabled for user traffic until an IP address to MAC address binding is received from the host by the discovery protocol, the network switch and the another network switch have no state synchronization regarding the MAC address;
advertising via a routing protocol a host route for the host; and
processing ARP or ND traffic from the host.
17. The non-transitory computer-readable medium or media of claim 16 wherein the steps further comprising: discarding broadcast, unknown unicast and multicast (BUM) traffic from the host.
18. The non-transitory computer-readable medium or media of claim 17 wherein the steps further comprising:
forwarding traffic within a subnet using the shared virtual MAC address.
19. The non-transitory computer-readable medium or media of claim 17 wherein the steps further comprising:
determining, using a Link Aggregation Control Protocol (LACP) or Bidirectional Forwarding Detection (BFD), liveness of a port of the host.
20. The non-transitory computer-readable medium or media of claim 19 wherein the BFD is a micro-BFD.