The Cisco IOS XR Software serves as a networking stack for communication. This section explains how applications on IOS XR can communicate with internal processes, and with servers or outside devices.

To communicate outside Cisco IOS XR, applications use the fwdintf interface address that maps to the loopback0 interface or a configured Gigabit Ethernet interface address.

To have an application on IOS XR communicate with its respective server outside IOS XR, you must configure an interface address as the source address on XR. The remote servers must configure this route address to reach the respective clients on IOS XR.

This section provides an example of configuring a Gigabit Ethernet interface address as the source address for external communication.

East-West communication on IOS XR is a mechanism by which applications hosted in containers interact with native XR applications (hosted in the XR control plane).

The following figure illustrates how a third-party application hosted on IOS XR interacts with the XR Control Plane.

The application sends data to the Forwarding Information Base (FIB) of IOS XR. The application is hosted in the east portion of IOS XR, while the XR control plane is located in the west region. Therefore, this form of communication between a third-party application and the XR control plane is termed as East-West (E-W) communication.

Third-party applications use this mode of communication to configure and manage containers, packages, and applications on IOS XR. In the future, this support could be extended to IOS XR, configured and managed by such third-party applications.

For a third-party application to communicate with IOS XR, the Loopback1 interface must be configured. This is explained in the following procedure.

1. Configure the Loopback1 interface on IOS XR.

   RP/0/RP0/CPU0:ios(config)# interface Loopback1 
   RP/0/RP0/CPU0:ios(config-if)# ipv4 address 8.8.8.8/32        
   RP/0/RP0/CPU0:ios(config-if)# no shut
   RP/0/RP0/CPU0:ios(config-if)# commit
   RP/0/RP0/CPU0:ios(config-if)# exit
   

2. Configure another Loopback interface that will be the East interface. You must configure this loopback interface to act as the TPA-facing interface, and Cisco IOS XR interacts with the TPA using this interface.

   RP/0/RP0/CPU0:ios(config)# interface Loopback100
   RP/0/RP0/CPU0:ios(config-if)# ipv4 address 15.1.1.1/32
   RP/0/RP0/CPU0:ios(config-if)# no shut
   RP/0/RP0/CPU0:ios(config-if)# commit
   RP/0/RP0/CPU0:ios(config-if)# exit
   

3. Verify the creation of the Loopback1 (West) and Loopback100 (East) interfaces.

   RP/0/RP0/CPU0:ios# show ipv4 interface brief
   Thu Nov 12 10:01:00.874 UTC
   
   Interface                      IP-Address      Status                Protocol
   Loopback0                      1.1.1.1         Up                    Up      
   Loopback1                      8.8.8.8         Up                    Up      
   Loopback100                    15.1.1.1        Up                    Up      
   GigabitEthernet0/0/0/0         192.164.168.10  Up                    Up      
   GigabitEthernet0/0/0/1         192.57.43.10    Up                    Up      
   GigabitEthernet0/0/0/2         unassigned      Shutdown              Down    
   MgmtEth0/RP0/CPU0/0            192.168.122.197 Up                    Up      
   

4. Configure the TPAs.

   RP/0/RP0/CPU0:ios(config)#tpa vrf default east-west loopback 1
   RP/0/RP0/CPU0:ios(config)#tpa vrf default address-family ipv4 default-route mgmt
   RP/0/RP0/CPU0:ios(config)#tpa vrf default address-family ipv4 update-source dataports loopback 100
   RP/0/RP0/CPU0:ios(config)#commit
   

5. Verify that a TPA interface that sets up Loopback100 as the East interface is configured.

   RP/0/RP0/CPU0:ios#sh run tpa
   Mon Jun 7 07:22:08.324 UTC
   tpa
   vrf default
   east-west Loopback1
   address-family ipv4
   default-route mgmt
   update-source dataports Loopback100
   !
   !
   !
   

6. Verify the E-W communication configuration by logging into the container and checking the routes. You can also ping the router-side East interface.

   Note	You can use the bash command to connect to the router and execute commands only in the testing environment.

   RP/0/RP0/CPU0:ios#bash
   Mon Jun 7 07:22:57.650 UTC
   [ios:~]$ docker exec -it a0 bash
   root@host:0_RP0:/# ip route
   default dev fwd_ew scope link src 15.1.1.1
   8.8.8.8 dev fwd_ew scope link src 15.1.1.1
   192.168.104.0/24 dev Mg0_RP0_CPU0_0 scope link src 192.168.104.10
   root@host:0_RP0:/# ping 8.8.8.8
   PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
   64 bytes from 8.8.8.8: icmp_seq=1 ttl=255 time=0.397 ms
   64 bytes from 8.8.8.8: icmp_seq=2 ttl=255 time=0.535 ms
   ^C
   --- 8.8.8.8 ping statistics ---
   2 packets transmitted, 2 received, 0% packet loss, time 2ms
   rtt min/avg/max/mdev = 0.397/0.466/0.535/0.069 ms
   root@host:0_RP0:/#

For more information on how to launch your own containers, see Using Docker for Hosting Applications on Cisco IOS XR topic. .

Cisco NCS 540 routers support the configuration of multiple VRFs. The applications hosted in third-party containers can communicate with VRFs configured on XR, after east-west communication has been enabled on the VRFs.

This section describes the configuration for creating mulitple VRFs, and enabling east-west communication between the applications and the VRFs.