Re: VXLAN multicast receive not working

Bernhard Schmidt [off-list ref] wrote:

quoted

quoted

The same VXLAN domain is defined on the Nexus 1000V and a VM is attached
to it. When I send some broadcast traffic down vxlan0 (i.e. ping
10.1.1.2 which generates an ARP request) the VM sees the packet just
fine.

When I do it the other way around (the VM sends a broadcast ARP for
10.1.1.3) I see a packet coming into eth1 on the multicast group, but
vxlan0 stays silent. 

I think I found a possible reason, my vxlan interface is on top of eth1

7: vxlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue
state UNKNOWN mode DEFAULT 
    link/ether 96:06:c6:cf:a0:2e brd ff:ff:ff:ff:ff:ff
    vxlan id 12340 group 239.0.0.42 dev eth1 port 32768 61000 ageing 300 

but the multicast group is joined only on eth0

Confirmed working as soon as eth0 can receive the group multicast
address (connected to the same VLAN), even if the vxlan0 interface is
still configured to eth1.

When swapping the configuration around using eth0 for the VXLAN
transport and eth1 for Management, the group is joined on eth1. It is
always joined where the default route points, so it looks like the
interface is not set at all.

# ip route add <group>/32 dev <vxlanintf>

works around the problem.

Bernhard