Chapter 10: VRouter

VRouter and VRouter Agent runs in COMPUTE.

Interfaces

• vhost0 is a tap interface between host-os and vrouter. vhost0 is the layer-3 interface used by host operating system. As part of setup, Contrail software migrates the IP configuration from ethernet port to vhost0.

• When networking stack of host-os sends packet on the vhost0 interface, they are received by vrouter module. Vrouter in turn routes the packet. When vrouter needs to send packet to networking stack of host-os, it transmits then through vhost0 interface.

• pkt0 is the tap interface between vrouter and vrouter-agent.

• Vrouter traps packets needing control processing such as flow-setup on this interface. Also, when agent uses the pkt0 interface to transmit control packets (ARP for example).

VRF (Virtual Routing and Forwarding)

• A VRF is created for each Virtual Network.
• Each VRF consists of 4 Routing Tables - ucindex(unicast), mcindex, l2index, u6index routing tables.
• VRF Name(default-domain:default-project:ip-fabric:__default__) for physical network/host VRF. This VRF is used for routing the data out to the internet/receives from it. Mostly it match with the routing table output .

vrfstats utility display the vrf statistics

cloud@devstack1:~$ sudo vrfstats  --get 1
Vrf: 1
Discards 0, Resolves 0, Receives 0, L2 Receives 0, Vrf Translates 0, Unknown Unicast Floods 0
Ecmp Composites 0, L2 Mcast Composites 0, Fabric Composites 0, Encap Composites 0, Evpn Composites 0
Udp Tunnels 0, Udp Mpls Tunnels 0, Gre Mpls Tunnels 0, Vxlan Tunnels 0
L2 Encaps 0, Encaps 2
GROs 0, Diags 0
Arp Virtual Proxys 0, Arp Virtual Stitchs 0, Arp Virtual Floods 0, Arp Physical Stitchs 0, Arp Tor Proxys 0, Arp Physical Floods 0

cloud@devstack1:~$

Routing Tables:

There are 4 routing table types, Unicast, Multicast, L2, IPv6 unicast. These routing tables are associated with the VRF,

Let us have a closer look on the unicast routing tables.

Routing tables(Private Network - 192.168.1.0):

• 169.254.169.254 entry for linklocal (To be confirmed)
• 192.168.1.0 - discard
• 192.168.1.1 - pkt0 (pkt0 is for vrouter agent -proxy for gateway)
• 192.168.1.2 - pkt0 (pkt0 is for vrouter agent - proxy dhcp server )
• 192.168.14 -- tap interface (VM)

Public Network (external network - 172.24.4.0)

• default route (0.0.0.0/0) -- vgw (virtual gatway)
• 169.254.169.254 entry for link local (To be confirmed)
• 172.24.4.0 -- discard
• 172.24.4.1 -- pkt0
• 172.24.4.2 -- pkt0
• 172.24.4.5 -- VM tap interface (floating IP is associated with a VM)

IP Fabric (Host Routing table)

• 172.24.4.0 ---- vhost0 --- Vgw (public Network VRF)
• 169.254.0.5 --- tap interface VM ---- for metadata (we can use this to SSH login to VM as backdoor)
• 10.0.1.6 ----- local ip vhost0
• 0.0.0.0/24 ---- 10.0.1.1 (gw ip)

I have set up the Simple Virtual Gateway, hence vgw interface is created and used. some references.

http://www.juniper.net/documentation/en_US/contrail3.2/topics/task/configuration/simple-gateway-support-vnc.html

Flows :

To be updated

VRouter Agent :

VRouter Introspect Port : 8085

In the VRouter introspect, we can get the following important data

Ref:

https://github.com/Juniper/contrail-controller/wiki/Contrail-Vrouter-Agent---Introspect