Overview of Easy Virtual Network (EVN) on Cisco Devices:

Easy Virtual Network (EVN) is an IP-based virtualization technology that provides end-to-end virtualization of two or more Layer-3 networks. We can use a single IP infrastructure to provide separate virtual networks whose traffic paths remain isolated from each other.

 

EVN builds on the existing IP-based virtualization mechanism known as VRF-Lite. EVN provides enhancements in path isolation, simplified configuration and management, and improved shared service support. EVN is backward compatible with the VRF-Lite solution to enable seamless network migration from VRF-Lite to EVN.

 

EVN supports IPv4, static routes, OSPFv2, and EIGRP for unicast routing, and PIM and MSDP for IPv4 Multicast routing. EVN also supports CEF and SNMP.

 

Supported Series of Cisco Devices:

 

Its proprietary, needs special line cards, offered on Catalyst 4500 and 6500 and the ASR 1000 only with special software requirements.
Restrictions for EVN

 

• An EVN trunk is allowed on any interface that supports 802.1q encapsulation, such as Fast Ethernet and Gigabit Ethernet.
• There are additional platform and line-card restrictions for the trunk. You will need to check Cisco Feature Navigator for supported platforms and line cards.
• A single IP infrastructure can be virtualized to provide up to 32 virtual networks end to end.
• If an EVN trunk is configured on an interface, you cannot configure VRF-Lite on the same interface.
• OSPFv3 is not supported; OSPFv2 is supported.
• The following protocols are not supported:
o IS-IS
o RIP
o Route replication is not supported with BGP
o certain SNMP set operations
• The following are not supported on an EVN trunk:
o access control lists (ACLs)
o BGP interface commands are not inherited
o IPv6 (except that IPv6 is supported on vnet global)
o NAT
o NetFlow
o WCCP

 

Benefits of EVN

 

• Reduced capital expenditures by not having to maintain separate physical infrastructures to keep traffic isolated. One IP network has two or more virtual networks with path isolation of the traffic in the networks, thereby saving the expense of additional hardware.
• Increased business flexibility, by easing the network integration of mergers, acquisitions, and business partners.
• Reduced complexity by decreasing the infrastructure requirements for maintaining traffic separation through the core of the network.
• They build on the existing mechanism known as Multi-VRF (VRF-Lite). EVN is compatible with VRF-Lite. See the EVN Compatibility with VRF-Lite section. EVN is recommended over VRF-Lite because EVN provides enhancements in path isolation, simplified configuration and management, and improved shared service support.
• In addition to maintaining traffic separation between business units within a company, there are other scenarios in which path isolation would be beneficial. Some examples follow:
o Guest access to the Internet–Restricting the guest
network access to the Internet, using a predetermined data
path through the customer’s network, and being able to
define a unique default route for Guest Internet bound
traffic.
o Network Admission Control (NAC) isolation–Isolating the
traffic sourced from a noncompliant desktop.
o Partner access–Restricting partners and contractors to
access network shared services that the customer allows,
such as Internet, e-mail, DNS, DHCP, or an application
server.
o Application and device isolation–Securing Data Center
services and devices by to a centralized firewall where the
traffic is subject to inspection.
o Outsourcing services–Separating data traffic of various
clients from each other.
o Scalable network–Restricting a portion of the network to
traffic that requires a very strict service level, which
can lower costs by providing those requirements only where
needed.
o Subsidiaries/mergers/acquisitions–Consolidating companies
or networks in stages, while enabling them to share
services, when required.
o Enterprise acting as a service provider–Autonomous groups
each requiring a separate network under a single authority.
An example is an airport authority supporting a virtual
network per airline.

 

Detailed Commands:

 

Command or Action Purpose
Step 1 enable
Example:
Router> enable Enables privileged EXEC mode.
• Enter your password if prompted.

 

Step 2 configure terminal
Example:
Router# configure terminal Enters global configuration mode.

 

Step 3 vrf definition vrf-name
Example:
Router(config)# vrf definition red Configures a VRF routing table instance and enters VRF configuration mode.

 

Step 4 vnet tag number
Example:
Router(config-vrf)# vnet tag 100 Specifies the global, numeric tag for the VRF.
• The same tag number must be configured for the same virtual network on each edge and trunk interface.

 

Step 5 description string
Example:
Router(config-vrf) description guest access (Optional) Describes a VRF to help the network administrator looking at the configuration file.

 

Step 6 address-family ipv4
Example:
Router(config-vrf) address-family ipv4 Enters address family configuration mode to configure a routing session using standard IP Version 4 address prefixes.

 

Step 7 exit-address-family
Example:
Router(config-vrf-af) exit-address-family Exits address family configuration mode.

 

Step 8 exit
Example:
Router(config-vrf)# exit Exits to the next highest configuration mode.

 

Step 9 vrf definition vrf-name
Example:
Router(config)# vrf definition blue Configures a VRF routing table instance and enters VRF configuration mode.

 

Step 10 vnet tag number
Example:
Router(config-vrf)# vnet tag 200 Specifies the global, numeric tag for the VRF.
• The same tag number must be configured for the same VRF on each edge and trunk interface.

 

Step 11 description string
Example:
Router(config-vrf) description Finance (Optional) Description of a VRF to help network administrator who is looking at configuration file.

 

Step 12 address-family ipv4
Example:
Router(config-vrf) address-family ipv4 Enters address family configuration mode to configure a routing session using standard IPv4 address prefixes.

 

Step 13 exit-address-family
Example:
Router(config-vrf-af) exit-address-family Exits address family configuration mode.

 

Step 14 exit
Example:
Router(config-vrf)# exit Exits to the next highest configuration mode.

 

Step 15 interface type number
Example:
Router(config)# interface gigabitethernet 1/1/1 Configures an interface type.

 

Step 16 ip address ip-address mask
Example:
Router(config-if)# ip address 10.1.1.1 255.255.255.0 Sets a primary address for the interface.

 

Step 17 vnet trunk [list vrf-list-name]
Example:
Router(config-if)# vnet trunk Defines a trunk interface.
• By default, all VRFs defined with the vrf definition command run on all trunk interfaces on the router. Therefore, VRF red and VRF blue are now running on this interface.
• Use the list vrf-list-name keyword/argument pair to restrict VRFs running on this trunk interface.

 

Step 18 vnet name vrf-name
Example:
Router(config-if)# vnet name red (Optional) Enters virtual network interface mode.
• The vnet command enters virtual network interface mode and allows you to configure features that apply to this VRF only, overriding global values. This step is not necessary if the global settings are acceptable for all of the VRFs on the interface.
• After this step, you would configure one or more eligible commands, such as ip ospf cost. (Not shown in this task.).

 

Step 19 exit-if-vnet
Example:
Router(config-if-vnet) exit-if-vnet Exits VRF interface configuration mode to interface configuration mode.

 

Step 20 no shutdown
Example:
Router(config-if) no shutdown Restarts an interface.

 

Step 21 exit
Example:
Router(config-if) exit Exits to the next highest configuration mode.

 

Step 22 router ospf process-id
Example:
Router(config)# router ospf 1 Configures an OSPF routing process and associates it with a VRF.
• This OSPF instance has no VRF, so it is vnet global.

 

Step 23 network ip-address wildcard area area-id
Example:
Router(config-router) network 10.0.0.0 255.255.255.0 area 0 Defines the interfaces on which OSPF runs and the area ID for those interfaces.

 

Step 24 exit
Example:
Router(config-router) exit Exits to the next highest configuration mode.

 

Step 25 router ospf process-id vrf vrf-name
Example:
Router(config)# router ospf 2 vrf red Configures an OSPF routing process and associates it with a VRF.
• Each VRF needs its own OSPF instance, so use a different process-id for each VRF.

 

Step 26 network ip-address wildcard area area-id
Example:
Router(config-router) network 10.0.0.0 255.255.255.0 area 0 Defines the interfaces on which OSPF runs and the area ID for those interfaces.

 

Step 27 exit
Example:
Router(config-router) exit Exits to the next highest configuration mode.

 

Step 28 router ospf process-id vrf vrf-name
Example:
Router(config)# router ospf 3 vrf blue Configures an OSPF routing process and associates it with a VRF.
• Each VRF needs its own OSPF instance, so use a different process-id for each VRF.

 

Step 29 network ip-address wildcard area area-id
Example:
Router(config-router) network 10.0.0.0 255.255.255.0 area 2 Defines the interfaces on which OSPF runs and the area ID for those interfaces.

 

Step 30 end
Example:
Router(config-vrf) end Ends the configuration session and returns to privileged EXEC mode.

 

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