Chapter 39. Starting a service within an isolated VRF network
With virtual routing and forwarding (VRF), you can create isolated networks with a routing table that is different to the main routing table of the operating system. You can then start services and applications so that they have only access to the network defined in that routing table.
39.1. Configuring a VRF device
To use virtual routing and forwarding (VRF), you create a VRF device and attach a physical or virtual network interface and routing information to it.
To prevent that you lock out yourself out remotely, perform this procedure on the local console or remotely over a network interface that you do not want to assign to the VRF device.
- You are logged in locally or using a network interface that is different to the one you want to assign to the VRF device.
vrf0connection with a same-named virtual device, and attach it to routing table
nmcli connection add type vrf ifname vrf0 con-name vrf0 table 1000 ipv4.method disabled ipv6.method disabled
enp1s0device to the
vrf0connection, and configure the IP settings:
nmcli connection add type ethernet con-name enp1s0 ifname enp1s0 master vrf0 ipv4.method manual ipv4.address 192.0.2.1/24 ipv4.gateway 192.0.2.254
This command creates the
enp1s0connection as a port of the
vrf0connection. Due to this configuration, the routing information are automatically assigned to the routing table
1000that is associated with the
If you require static routes in the isolated network:
Add the static routes:
nmcli connection modify enp1s0 +ipv4.routes "198.51.100.0/24 192.0.2.2"
This adds a route to the
198.51.100.0/24network that uses
192.0.2.2as the router.
Reload the connection:
nmcli connection up enp1s0
Display the IP settings of the device that is associated with
ip -br addr show vrf vrf0enp1s0 UP 192.0.2.15/24
Display the VRF devices and their associated routing table:
ip vrf showName Table ----------------------- vrf0 1000
Display the main routing table:
ip route showdefault via 192.168.0.1 dev enp1s0 proto static metric 100
Display the routing table
# ip route show table 1000default via 192.0.2.254 dev enp1s0 proto static metric 101 broadcast 192.0.2.0 dev enp1s0 proto kernel scope link src 192.0.2.1 192.0.2.0/24 dev enp1s0 proto kernel scope link src 192.0.2.1 metric 101 local 192.0.2.1 dev enp1s0 proto kernel scope host src 192.0.2.1 broadcast 192.0.2.255 dev enp1s0 proto kernel scope link src 192.0.2.1 198.51.100.0/24 via 192.0.2.2 dev enp1s0 proto static metric 101
defaultentry indicates that services that use this routing table, use
192.0.2.254as their default gateway and not the default gateway in the main routing table.
tracerouteutility in the network associated with
vrf0to verify that the utility uses the route from table
ip vrf exec vrf0 traceroute 203.0.113.1traceroute to 203.0.113.1 (203.0.113.1), 30 hops max, 60 byte packets 1 192.0.2.254 (192.0.2.254) 0.516 ms 0.459 ms 0.430 ms ...
The first hop is the default gateway that is assigned to the routing table
1000and not the default gateway from the system’s main routing table.
39.2. Starting a service within an isolated VRF network
You can configure a service, such as the Apache HTTP Server, to start within an isolated virtual routing and forwarding (VRF) network.
Services can only bind to local IP addresses that are in the same VRF network.
You configured the
You configured Apache HTTP Server to listen only on the IP address that is assigned to the interface associated with the
Display the content of the
systemctl cat httpd... [Service] ExecStart=/usr/sbin/httpd $OPTIONS -DFOREGROUND ...
You require the content of the
ExecStartparameter in a later step to run the same command within the isolated VRF network.
/etc/systemd/system/httpd.service.d/override.conffile with the following content:
[Service] ExecStart= ExecStart=/usr/sbin/ip vrf exec vrf0 /usr/sbin/httpd $OPTIONS -DFOREGROUND
To override the
ExecStartparameter, you first need to unset it and then set it to the new value as shown.
systemctl restart httpd
Display the process IDs (PID) of
pidof -c httpd1904 ...
Display the VRF association for the PIDs, for example:
ip vrf identify 1904vrf0
Display all PIDs associated with the
# ip vrf pids vrf0 1904 httpd ...