Dell Networking SONiC: How to Configure Virtual Routing and Forwarding

Summary: This article explains how to configure Virtual Routing and Forwarding (VRF) in Dell Networking SONiC. This article uses a switch running Dell SONiC 4.1.

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Instructions

 
Prerequisites
We are using standard interface naming to demonstrate the Concepts. See Dell article Dell Networking S-Series: Basic Interface Configuration - SONiC 4.0 for more information regarding interface naming


Index:

Introduction Sample Configuration
 

Introduction

Virtual Routing and Forwarding (VRF) partitions a physical router into multiple virtual routers. The control and data plane are isolated in each virtual router; traffic does not flow across virtual routers. VRF allows multiple instances of independent routing tables to co-exist within the same router simultaneously.
  • The number of maximum configurable VRFs in a Dell SONiC switch depends on the platform.
  • Remove any existing IP address from an L3 interface before assigning it to a VRF

Dell SONiC supports the following VRF instances:

  • Default VRF instance
  • Nondefault VRF instances
  • Management VRF instance
The below table shows supported features in management, default, and nondefault VRF instances:
 
Feature Management VRF Default VRF Nondefault VRF
BGP No Yes Yes
ICMP or PING Yes Yes Yes
NTP client Yes Yes Yes
NTP server Yes Yes No
SCP client Yes Yes Yes
Traceroute Yes Yes Yes
 

Default VRF

In Dell SONiC, by default, the system initially assigns all physical interfaces including management interface and all logical interfaces to the default VRF instance.

    Management VRF

    The management VRF provides a separate mgmt routing table for an out-of-band management network that is different from the default in-band data-plane network. A dedicated management VRF provides an isolated routing table for the management interface when accessing the switch using SSH.
    • NTP uses the management VRF by default; if the management VRF is not configured, NTP uses the default VRF.
    • The management VRF does not support IP services, such as TFTP and FTP.
    • DNS is supported.

    Management VRF Configuration Syntax:

    Enable Management VRF and move Management port to Management VRF mgmt. 
    admin@DELLSONiC:~$ sonic-cli
DELLSONiC# configure
DELLSONiC(config)# ip vrf mgmt

    Verify  
    DELLSONiC# show ip vrf mgmt
VRF-NAME            INTERFACES
----------------------------------------------------------------
mgmt                Management0

    Delete Management VRF and return the management interface to default VRF.  
    admin@DELLSONiC:~$ sonic-cli
DELLSONiC# configure
DELLSONiC(config)# no ip vrf mgmt
     

    Non-default VRF

    To separate traffic, we can configure nondefault VRFs in DELL SONiC. We can bind physical Ethernet, loopback, port channel, and VLAN interfaces to a nondefault VRF.
    • Non-default vrf-name is up to 15 alphanumeric characters
    • VRF name should start with the prefix Vrf; for example, VrfRED, Vrf10, Vrf_BLUE.
    • Management port cannot be configured as part of Non-default VRF


    Non-default VRF Configuration Syntax

    Create VRF 
    admin@DELLSONiC:~$ sonic-cli
DELLSONiC# configure
DELLSONiC(config)# ip vrf Vrf_NAME

    Bind a Layer 3 interface, vlan, portchannel, loopback to VRF: 
    admin@DELLSONiC:~$ sonic-cli
DELLSONiC# configure
DELLSONiC(config)# interface <Eth slot/port><Vlan ID><PortChannel ID><Eth slot/port.subport><Loopback ID>
DELLSONiC(config-if-XXXX)# ip vrf forwarding Vrf_NAME

    Verify VRF 
    admin@DELLSONiC:~$ sonic-cli
DELLSONiC# show ip vrf
VRF-NAME            INTERFACES
----------------------------------------------------------------
Vrf_NAME            Vlan10
default

    Unbind an interface from a VRF. 
    admin@DELLSONiC:~$ sonic-cli
DELLSONiC# configure
DELLSONiC(config)# interface <Eth slot/port><Vlan ID><PortChannel ID><Eth slot/port.subport><Loopback ID>
DELLSONiC(config-if-XXXX)# no ip vrf forwarding Vrf_NAME

    Delete a VRF. 
    admin@DELLSONiC:~$ sonic-cli
DELLSONiC# configure
DELLSONiC(config)# no ip vrf Vrf_NAME
     

    Sample Configuration

    To understand the basic VRF configuration, let us review the following topology as shown. 

    VRF configuration

    Goal: Our goal is to ensure traffic of VLAN 10 can only communicate with VLAN 20 and vice versa. VLAN 30 only communicates with VLAN 40 and vice versa.

    The VLANs are already created, respective ports are already assigned to the VLANs, and interfaces are unshut in Dell Networking SONiC Switch. 

    To know more regarding VLAN configuration, see article Dell Networking SONiC: How to Create a VLAN and Assign it to Trunk and Access Switchports
     

    Vrf_RED Configuration
     
    Vrf_BLUE Configuration
     

    Enter Dell Management framework CLI and configure mode 
    admin@DELLSONiC:~$ sonic-cli
DELLSONiC# configure
    Enter Dell Management framework CLI and configure mode 
    admin@DELLSONiC:~$ sonic-cli
DELLSONiC# configure

    Create VRF Vrf_RED 
    DELLSONiC(config)# ip vrf Vrf_RED
    Create VRF Vrf_BLUE 
    DELLSONiC(config)# ip vrf Vrf_BLUE

    Bind VLAN 10 to Vrf_BLUE and assign IP address 
    DELLSONiC(config)# interface Vlan 10
DELLSONiC(config-if-Vlan10)# ip vrf forwarding Vrf_RED
DELLSONiC(config-if-Vlan10)# ip address 10.0.0.1/24
DELLSONiC(config-if-Vlan10)# exit
    Bind VLAN 30 to Vrf_BLUE and assign IP address 
    DELLSONiC(config)# interface Vlan 30
DELLSONiC(config-if-Vlan30)# ip vrf forwarding Vrf_BLUE
DELLSONiC(config-if-Vlan30)# ip address 30.0.0.1/24
DELLSONiC(config-if-Vlan30)# exit

    Bind VLAN 20 to Vrf_BLUE and assign IP address 
    DELLSONiC(config)# interface Vlan 20
DELLSONiC(config-if-Vlan20)# ip vrf forwarding Vrf_RED
DELLSONiC(config-if-Vlan20)# ip address 20.0.0.1/24
DELLSONiC(config-if-Vlan20)# end
    Bind VLAN 40 to Vrf_BLUE and assign IP address 
    DELLSONiC(config)# interface Vlan 40
DELLSONiC(config-if-Vlan40)# ip vrf forwarding Vrf_BLUE
DELLSONiC(config-if-Vlan40)# ip address 40.0.0.1/24
DELLSONiC(config-if-Vlan40)# end

    Let us verify the configuration. 
    DELLSONiC# show ip vrf
VRF-NAME            INTERFACES
----------------------------------------------------------------
Vrf_BLUE            Vlan30
                    Vlan40
Vrf_RED             Vlan10
                    Vlan20
    		 
    DELLSONiC# show ip interfaces
Flags: U-Unnumbered interface, A-Anycast IP
-----------------------------------------------------------------------------------------------------------------
Interface            IP address/mask                              VRF                 Admin/Oper     Flags
-----------------------------------------------------------------------------------------------------------------
Vlan10               10.0.0.1/24                                  Vrf_RED             up/up
Vlan20               20.0.0.1/24                                  Vrf_RED             up/up
Vlan30               30.0.0.1/24                                  Vrf_BLUE            up/up
Vlan40               40.0.0.1/24                                  Vrf_BLUE            up/up

    We can see Vrf_BLUE has VLAN 30 and VLAN 40. Vrf_RED has VLAN 10 and VLAN 20.

    Let us compare the routing table for both VRF:
    Vrf_RED 
    DELLSONiC# show ip route vrf Vrf_RED
Codes:  K - kernel route, C - connected, S - static, B - BGP, O - OSPF
        > - selected route, * - FIB route, q - queued route, r - rejected route
       Destination        Gateway                                                                    Dist/Metric   Last Update
--------------------------------------------------------------------------------------------------------------------------------
 C>*   10.0.0.0/24        Direct                          Vlan10                                     0/0           00:31:42 ago
 C>*   20.0.0.0/24        Direct                          Vlan20                                     0/0           00:31:31 ago
     
    Vrf_BLUE 
    DELLSONiC# show ip route vrf Vrf_BLUE
Codes:  K - kernel route, C - connected, S - static, B - BGP, O - OSPF
        > - selected route, * - FIB route, q - queued route, r - rejected route
       Destination        Gateway                                                                    Dist/Metric   Last Update
--------------------------------------------------------------------------------------------------------------------------------
 C>*   30.0.0.0/24        Direct                          Vlan30                                     0/0           00:24:28 ago
 C>*   40.0.0.0/24        Direct                          Vlan40                                     0/0           00:10:56 ago

    Affected Products

    Enterprise SONiC Distribution, PowerSwitch E3200-ON Series, Dell EMC Networking N3200-ON, PowerSwitch S5212F-ON, PowerSwitch S5224F-ON, PowerSwitch S5232F-ON, PowerSwitch S5248F-ON, PowerSwitch S5296F-ON, PowerSwitch Z9264F-ON, PowerSwitch Z9332F-ON , PowerSwitch Z9432F-ON ...
    Article Properties
    Article Number: 000218893
    Article Type: How To
    Last Modified: 10 Nov 2023
    Version:  5
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