Signaling aliasing capability in data centers

Abstract

Techniques are described for signaling aliasing capability between routers in a multi-tenant data center that uses VPNs, such as Ethernet VPNs. In the multi-tenant data center, two or more PE routers may be connected to a CE router by a multi-homed L2 segment in an all-active mode. Aliasing refers to the ability of a PE router to signal that it can reach a given multi-homed L2 segment even when the PE router has learned no MAC addresses over that multi-homed L2 segment. The PE routers on the multi-homed L2 segment advertise aliasing capability using a route advertisement on a per-L2 segment basis. When the multi-tenant data center uses global VPN identifiers, no additional information is needed by a remote PE to build an ECMP next hop to the PE routers that support aliasing, and transmission of a route advertisement on a per-VPN basis may be suppressed.

What is claimed is: 
     
         1 . A system comprising:
 two or more provider edge (PE) routers included in a layer two virtual private network (L2 VPN) established between a first site and a second site of a multi-tenant data center, wherein the two or more PE routers are connected to a customer edge (CE) router of the first site by a multi-homed L2 network segment associated with a particular customer, and wherein the two or more PE routers are configured to operate in an all-active mode in which all of the PE routers forward L2 traffic from at least one remote PE router included in the L2 VPN to the CE router over the multi-homed L2 network segment;   a first PE router of the two or more PE routers configured to receive, from the CE router, a packet with an L2 address associated with the CE router, and send, to the at least one remote PE router, a route advertisement including the L2 address associated with the CE router; and   a second PE router of the two or more PE routers configured to send, to the at least one remote PE router using a routing protocol, an auto-discovery (AD) route advertisement associated with the multi-homed L2 network segment indicating whether the second PE router supports aliasing for the multi-homed L2 network segment to reach the L2 address associated with the CE router without having learned the L2 address over the multi-homed L2 network segment, and, when the L2 VPN uses a global identifier, suppress transmission of another AD route advertisement associated with a VPN instance of the L2 VPN.   
     
     
         2 . The system of  claim 1 ,
 wherein the L2 VPN comprises an Ethernet virtual private network (EVPN) and the multi-homed L2 network segment comprises a multi-homed Ethernet segment (ES), and   wherein the AD route advertisement associated with the multi-homed L2 network segment comprises a per-ES auto-discovery (AD) route advertisement that includes an Ethernet Segment Identifier (ESI) Label Extended Community with an aliasing bit, wherein the aliasing bit being set indicates that the second PE router supports aliasing for the multi-homed ES, and the aliasing bit being reset indicates that the second PE router does not support aliasing for the multi-homed ES.   
     
     
         3 . A method comprising:
 establishing a layer two virtual private network (L2 VPN) between two or more provider edge (PE) routers and at least one remote PE router, wherein the two or more PE routers are connected to a customer edge (CE) router of a customer site by a multi-homed L2 network segment in an all-active mode;   receiving, by a first PE router of the two or more PE routers and from the CE router, a packet with an L2 address associated with the CE router;   sending, by the first PE router and to the at least one remote PE router, a route advertisement including the L2 address associated with the CE router; and   sending, by at least a second PE router of the two or more PE routers to the at least one remote PE router using a routing protocol, an auto-discovery (AD) route advertisement associated with the multi-homed L2 network segment indicating whether the second PE router supports aliasing for the multi-homed L2 network segment.   
     
     
         4 . The method of  claim 3 , wherein the L2 VPN uses a global identifier, the method further comprising suppressing, by the second PE router, transmission of another AD route advertisement associated with an instance of the L2 VPN. 
     
     
         5 . The method of  claim 3 , wherein the L2 VPN uses a local identifier or comprises a Multi-Protocol Label Switching (MPLS) based L2 VPN, the method further comprising, based on the second PE router supporting aliasing for the multi-homed L2 network segment, sending, by the second PE router and to the at least one remote PE router, another AD route advertisement associated with an instance of the L2 VPN indicating one of the local identifier or an aliasing label. 
     
     
         6 . The method of  claim 3 ,
 wherein the L2 VPN comprises an Ethernet virtual private network (EVPN) and the multi-homed L2 network segment comprises a multi-homed Ethernet segment (ES), and   wherein the AD route advertisement associated with the multi-homed L2 network segment comprises a per-ES AD route advertisement that includes an Ethernet Segment Identifier (ESI) Label Extended Community with an aliasing bit, wherein the aliasing bit being set indicates that the second PE router supports aliasing for the multi-homed ES, and the aliasing bit being reset indicates that the second PE router does not support aliasing for the multi-homed ES.   
     
     
         7 . The method of  claim 3 , wherein the L2 VPN is established between a first site and a second site of a multi-tenant data center, wherein the customer site comprises the first site of the multi-tenant data center, and wherein the at least one remote PE router is connected to another CE router of the second site. 
     
     
         8 . A system comprising:
 two or more provider edge (PE) routers included in a layer two virtual private network (L2 VPN), wherein the two or more PE routers are connected to a customer edge (CE) router of a customer site by a multi-homed L2 network segment in an all-active mode;   a first PE router of the two or more PE routers configured to receive, from the CE router, a packet with an L2 address associated with the CE router, and send, to the at least one remote PE router, a route advertisement including the L2 address associated with the CE router; and   a second PE router of the two or more PE routers configured to send, to at least one remote PE router included in the L2 VPN, an auto-discovery (AD) route advertisement associated with the multi-homed L2 network segment indicating whether the second PE router supports aliasing for the multi-homed L2 network segment.   
     
     
         9 . The system of  claim 8 , wherein the L2 VPN uses a global identifier, and wherein the second PE router is further configured to suppress transmission of another AD route advertisement associated with an instance of the L2 VPN. 
     
     
         10 . The system of  claim 8 , wherein the L2 VPN uses a local identifier or comprises a Multi-Protocol Label Switching (MPLS) based L2 VPN, and wherein, based on the second PE router supporting aliasing for the multi-homed L2 network segment, the second PE router is further configured send, to the at least one remote PE router, another AD route advertisement associated with an instance of the L2 VPN indicating one of the local identifier or an aliasing label. 
     
     
         11 . The system of  claim 8 ,
 wherein the L2 VPN comprises an Ethernet virtual private network (EVPN) and the multi-homed L2 network segment comprises a multi-homed Ethernet segment (ES), and   wherein the AD route advertisement associated with the multi-homed L2 network segment comprises a per-ES AD route advertisement that includes an Ethernet Segment Identifier (ESI) Label Extended Community with an aliasing bit, wherein the aliasing bit being set indicates that the second PE router supports aliasing for the multi-homed ES, and the aliasing bit being reset indicates that the second PE router does not support aliasing for the multi-homed ES.   
     
     
         12 . A method comprising:
 establishing a layer two virtual private network (L2 VPN) between two or more provider edge (PE) routers and a remote PE router, wherein the two or more PE routers are connected to a customer edge (CE) router of a customer site by a multi-homed L2 network segment in an all-active mode;   receiving, by the remote PE router and from a first PE router of the two or more PE routers, a route advertisement including a L2 address associated with the CE router;   receiving, by the remote PE router and from at least a second PE router of the two or more PE routers, an auto-discovery (AD) route advertisement associated with the multi-homed L2 network segment indicating whether the second PE router supports aliasing for the multi-homed L2 network segment; and   based on the AD route advertisement indicating that the second PE router supports aliasing for the multi-homed L2 network segment, building, by the remote PE router, a next hop to at least the first and second PE routers of the two or more PE routers to reach the L2 address associated with the CE router over the multi-homed L2 network segment.   
     
     
         13 . The method of  claim 12 , wherein the L2 VPN uses a global identifier, the method further comprising:
 receiving the global identifier included in the route advertisement from the first PE router; and   building the next hop to at least the first and second PE routers using the global VNI.   
     
     
         14 . The method of  claim 12 , wherein the L2 VPN uses a local identifier or comprises a Multi-Protocol Label Switching (MPLS) based L2 VPN, the method further comprising:
 receiving, from the second PE router, another AD route advertisement associated with an instance of the L2 VPN indicating one of the local identifier or an aliasing label; and   building the next hop to at least the first and second PE routers using the one of the local identifier the aliasing label.   
     
     
         15 . The method of  claim 12 ,
 wherein the L2 VPN comprises an Ethernet virtual private network (EVPN) and the multi-homed L2 network segment comprises a multi-homed Ethernet segment (ES), and   wherein the AD route advertisement associated with the multi-homed L2 network segment comprises a per-ES AD route advertisement that includes an Ethernet Segment Identifier (ESI) Label Extended Community with an aliasing bit, wherein the aliasing bit being set indicates that the second PE router supports aliasing for the multi-homed ES, and the aliasing bit being reset indicates that the second PE router does not support aliasing for the multi-homed ES.   
     
     
         16 . The method of  claim 12 , wherein the L2 VPN is established between a first site and a second site of a multi-tenant data center, wherein the customer site comprises the first site of the multi-tenant data center, and wherein the remote PE router is connected to another CE router of the second site. 
     
     
         17 . A router comprising:
 a memory; and   one or more processors in communication with the memory and configured to:
 establish a layer two virtual private network (L2 VPN) between the router and two or more provider edge (PE) routers connected to a customer edge (CE) router of a customer site by a multi-homed L2 network segment in an all-active mode; 
 receive, from a first PE router of the two or more PE routers, a route advertisement including a L2 address associated with the CE router; 
 receive, from at least a second PE router of the two or more PE routers, an auto-discovery (AD) route advertisement associated with the multi-homed L2 network segment indicating whether the second PE router supports aliasing for the multi-homed L2 network segment; and 
 based on the AD route advertisement indicating that the second PE router supports aliasing for the multi-homed L2 network segment, build a next hop to at least the first and second PE routers of the two or more PE routers to reach the L2 address associated with the CE router over the multi-homed L2 network segment. 
   
     
     
         18 . The router of  claim 17 , wherein the L2 VPN uses a global identifier, and wherein the one or more processors are further configured to:
 receive the global identifier included in the route advertisement from the first PE router; and   build the next hop to at least the first and second PE routers using the global VNI.   
     
     
         19 . The router of  claim 17 , wherein the L2 VPN uses a local identifier or comprises a Multi-Protocol Label Switching (MPLS) based L2 VPN, and wherein the one or more processors are further configured to:
 receive, from the second PE router, another AD route advertisement associated with an instance of the L2 VPN indicating one of the local identifier or an aliasing label; and   build the next hop to at least the first and second PE routers using the one of the local identifier the aliasing label.   
     
     
         20 . The router of  claim 17 ,
 wherein the L2 VPN comprises an Ethernet virtual private network (EVPN) and the multi-homed L2 network segment comprises a multi-homed Ethernet segment (ES), and   wherein the AD route advertisement associated with the multi-homed L2 network segment comprises a per-ES AD route advertisement that includes an Ethernet Segment Identifier (ESI) Label Extended Community with an aliasing bit, wherein the aliasing bit being set indicates that the second PE router supports aliasing for the multi-homed ES, and the aliasing bit being reset indicates that the second PE router does not support aliasing for the multi-homed ES.