Setting up FRR for VRFs (like we have in the ICM lab)

[John Krueger]

Here's a step-by-step to build a FRR router like we have in the lab.  I am still trying to figure out an elegant way to persist this configuration across reboots.  It doesn't seem like there's a reasonable way to add network namespaces and dummy interfaces to the standard network startup files (either through netplan or in /etc/network/interfaces), so you may just have to create a script for the interface/vlan/netns config and run it from /etc/rc.local or something like that. 

Many thanks to David Belmonte Sola, the content developer that made this work in the first place and sent me his notes.

1. Install FRR - http://docs.frrouting.org/en/latest/installation.html
2. Configure Zebra to use Linux netns:
   1. Edit /etc/frr/daemons
   2. Modify {zebra_options=“-A 127.0.0.1 -s 9000000”} to {zebra_options=“A 127.0.0.1 -s 9000000 -n”}
      1. The “-n” (or —vrfnetns” option starts zebra with support for VRF backend based on the Linux Network Namespace infrastructure.
3. Configure VLAN interfaces
   1. Load the VLAN kernel Module
      1. # modprobe 8021q
   2. Tell the system to load the VLAN kernel Module on reboot:
      1. # echo “8021q” >> /etc/modules
   3. Configure the VLANs with the vconfig tool
      1. 1. Syntax: vconfig add <interface name> <VLAN ID>
         2. This requires the VLAN tools to be installed on your system.  For Ubuntu, “apt install vlan” will get them.
      2. # vconfig add ens224 10
      3. # vconfig add ens224 20
      4. # vconfig add ens224 30
      5. # vconfig add ens224 40
4. Create dummy interfaces to use as loopback interfaces for the VRFs
   1. Load the Dummy Network Interface Module
      1. # modprobe dummy
   2. Tell the system to load the Dummy Network Interface module on reboot:
      1. # echo “dummy” >> /etc/modules
   3. Create dummy interfaces
      1. # ip link add dummy0 type dummy
      2. # ip link add dummy1 type dummy
      3. # ip link add dummy2 type dummy
      4. # ip link add dummy3 type dummy
5. Create namespaces for VRFs
   1. # ip netns add red
   2. # ip netns add blue
6. Assign the interfaces to Network Namespaces
   1. # ip link set ens224.10 netns red
   2. # ip link set ens224.30 netns red
   3. # ip link set dummy0 netns red
   4. # ip link set dummy2 netns red
   5. # ip link set ens224.20 netns blue
   6. # ip link set ens224.40 netns blue
   7. # ip link set dummy1 netns blue
   8. # ip link set dummy3 nets blue
7. Bring up the interfaces
   1. # ip netns exec red ip link set ens224.10 up
   2. # ip netns exec red ip link set ens224.30 up
   3. # ip netns exec red ip link set dummy0 up
   4. # ip netns exec red ip link set dummy2 up
   5. # ip netns exec blue ip link set ens224.20 up
   6. # ip netns exec blue ip link set ens224.40 up
   7. # ip netns exec blue ip link set dummy1 up
   8. # ip netns exec blue ip link set dummy3 up
8. Enable Network Namespace forwarding
   1. 1. “ip netns exec <namespace> <command>” executes a command in the context of the network namespace for applications that are not explicitly namespace aware.
   2. # ip netns exec red /bin/bash // this executes the bash shell in the red network namespace
   3. # echo 1 > /proc/sys/net/ipv4/ip_forward // this will enable IPv4 packet  forwarding for the namespace
   4. # exit // this will exit the bash shell running in the red namespace
   5. # ip netns exec blue /bin/bash
   6. # echo 1 > /proc/sys/net/ipv4/ip_forward
   7. # exit
9. Restart FRR to detect namespaces and interfaces
   1. Depending on your distribution what service subsystem you may prefer
      1. # /etc/init.d/frr restart
      2. # systemctl restart frr
10. Configure FRR
    1. Enter configuration mode
       1. # vtysh // this enters the FRR configuration shell
       2. > configure terminal // this enters configuration mode from the terminal
    2. Create interfaces in VRF red:
       1. > interface ens224.10 vrf red // enters the ens224.10 interface configuration in VRF red
       2. > IP address 192.168.10.1/24 // sets the IPv4 address and net mask
       3. > interface dummy0 vrf red
       4. > IP address 10.0.10.1/24
       5. > interface ens224.30 vrf red
       6. > IP address 192.168.30.1/24
       7. > interface dummy2 vrf red
       8. > IP address 10.0.30.1/24
    3. Create interfaces in VRF blue
       1. > interface ens224.20 vrf blue
       2. > IP address 192.168.20.1/24
       3. > interface dummy1 vrf blue
       4. > IP address 10.0.20.1/24
       5. > interface ens224.40 vrf blue
       6. > IP address 192.168.40.1/24
       7. > interface dummy3 vrf blue
       8. > IP address 10.0.40.1/24
    4. Configure BGP on the red VRF instance
       1. > router bgp 10 vrf red
       2. > bgp router-id 192.168.10.1
       3. > bgp log-neighbor-changes
       4. > neighbor 192.168.10.2 remote-as 100
       5. > address-family ipv4 unicast
       6. > redistribute connected
       7. > exit-address-family
    5. Configure BGP on the blue VRF instance
       1. > router bgp 20 vrf blue
       2. > bgp router-id 192.168.20.1
       3. > bgp log-neighbor-changes
       4. > neighbor 192.168.20.2 remote-as 100
       5. > address-family ipv4 unicast
       6. > redistribute connected
       7. > exit-address-family
    6. Exit Router Configuration:
       1. > exit
    7. Exit configuration mode:
       1. Exit
    8. Write the configuration changes
       1. > write
    9. Exit configuration mode
       1. > exit