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Routing configuration between VRs

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TitleRouting configuration between VRs
How to configure Inter-VR Routing (routing between two virtual routers) in the same switch
  • EXOS 15.6 and above
  • IPv4

Inter-VR Routing for IPv4 Unicast Static Routes:

  • In  EXOS 15.6 there is a new feature that allows static routing between two virtual routers.
  • Allows for routing of IPv4 unicast packets between Virtual Routers via static routes. This is referred to as Inter-VR Routing. The next hop gateway of a static route may reside in a Virtual LAN belonging to a different Virtual Router from the Virtual Router of the static route.When inter-vr routing is configured the gateway address should be different from VLAN IP of the switch and it should be reachable (ARP resolved) from the switch.
  • Inter-VR routing is supported for hardware forwarding and software forwarding of IPv4 unicast packets, including Equal-Cost Multi-Path (ECMP).
Example Command: "configure iproute add <network> <next hop> vlan <egress_vlan> vr <ingress_vr_name>"

Note that the “vlan <egress_vlan>”, specifying the outgoing VLAN of the next hop gateway, refers to a VLAN belonging to a different VR because Inter-VR routing is desired. The “vr <ingress_vr_name>” of the static route command refers to which VR’s route table the route is added.

Consider the following Network Topology:

Inter VR Routing Topology

In the topology above VLAN v1 belongs to VR vr1, and VLAN v2 belongs to VR vr2. The final two commands add Inter-VR routes between VR vr1 and VR vr2. The resulting behavior is that IPv4 unicast packets with a source IP address in subnet in VR vr1, and a destination IP address in subnet, are forwarded to gateway belonging to VLAN v2 in VR vr2. Reverse packets are forwarded to gateway belonging to VLAN v1 in VR vr1.

create vr "vr1"
create vr "vr2"
create vlan "v1" vr vr1
create vlan "v2" vr vr2
configure vlan v1 tag 10
configure vlan v2 tag 20
configure vlan v1 add ports 1 tagged
configure vlan v2 add ports 2 tagged
configure vlan v1 ipaddress
configure vlan v2 ipaddress
enable ipforwarding vlan v1
enable ipforwarding vlan v2

configure iproute add vlan v2 vr vr1
configure iproute add vlan v1 vr vr2

The example above is for packets routed through a gateway to a remote subnet. But Inter-VR routing can also be accomplished to/from a host adjacent to the switch, i.e. hosts connected to locally attached networks, by adding a /32 host route. In the example network above, to have packets from VR1 route to a host/server in VR2 directly on the subnet, such as, the following CLI command can be used by specifying

configure iproute add vlan v2 vr vr1
Additional notes
  • In EXOS 15.5 and older, it is not possible to route between VRs.
  • Inter-VR routing for IPv6 is not currently supported.  If attempting to add an inter-VR IPv6 route a CLI error will be printed like the following:
SWITCH.16 # conf iproute add 2001::192:168:2:66/128 2001::192:168:2:66 vlan v2 vr "vr1" 
ERROR: Egress VLAN belongs to a different Virtual Router




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