[linux-vrf-core] Using the same IP address for different vrf

[Affandi I. <aff...@gm...>]

Hi all,

I experience something strange if I configure different interface
using the same IP address (on different VRF)

ip addr
27: eth1.223: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue vrf 23
    link/ether 00:02:55:7b:20:75 brd ff:ff:ff:ff:ff:ff
    inet 10.11.3.2/24 scope global eth1.223
28: eth1.224: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue vrf 24
    link/ether 00:02:55:7b:20:75 brd ff:ff:ff:ff:ff:ff
    inet 10.11.3.2/24 scope global eth1.224

ip route
10.11.3.0/24 dev eth1.223  proto kernel  scope link  src 10.11.3.2  vrf 23
default via 10.11.3.1 dev eth1.223  vrf 23
10.11.3.0/24 dev eth1.224  proto kernel  scope link  src 10.11.3.2  vrf 24
default via 10.11.3.1 dev eth1.224  vrf 24
-----------------------------------------------
test# chvrf 24 ping 10.11.3.1
PING 10.11.3.1 (10.11.3.1) 56(84) bytes of data.
64 bytes from 10.11.3.1: icmp_seq=3D1 ttl=3D255 time=3D1.04 ms
64 bytes from 10.11.3.1: icmp_seq=3D2 ttl=3D255 time=3D0.387 ms
64 bytes from 10.11.3.1: icmp_seq=3D3 ttl=3D255 time=3D0.503 ms

test# chvrf 23 ping 10.11.3.1
PING 10.11.3.1 (10.11.3.1) 56(84) bytes of data.
--- 10.11.3.1 ping statistics ---
7 packets transmitted, 0 received, 100% packet loss, time 5999ms
------------------------------------------
as you can see, I can ping vrf 24 but not vrf 23. BUT, if I wait for a
while I can ping vrf 23 but not vrf 24. (see below)
------------------------------------------
test# chvrf 23 ping 10.11.3.1
PING 10.11.3.1 (10.11.3.1) 56(84) bytes of data.
64 bytes from 10.11.3.1: icmp_seq=3D1 ttl=3D255 time=3D0.811 ms
64 bytes from 10.11.3.1: icmp_seq=3D2 ttl=3D255 time=3D0.369 ms
64 bytes from 10.11.3.1: icmp_seq=3D3 ttl=3D255 time=3D0.359 ms

test# chvrf 24 ping 10.11.3.1
PING 10.11.3.1 (10.11.3.1) 56(84) bytes of data.

--- 10.11.3.1 ping statistics ---
2 packets transmitted, 0 received, 100% packet loss, time 999ms
---------------------

Is there any limitation that we can't use the same IP address for
different vrf? The reason I want to try it is to support the MPLS,
using the same IP address for different VRF.

/affandi