Hello everybody,
I am facing the following problem when trying to send multicast through
a tunnel.
Basically I would like to send datagrams having the following format:
outer IP inner IP
Src Dst Src Dst
195.2.3.180 195.2.3.179 195.2.3.180 224.1.2.3 <<< data >>>
So, I did the following settings:
# ip addr
...
2: eth0: <BROADCAST,UP> mtu 1500 qdisc pfifo_fast qlen 100
link/ether 01:02:03:04:05:06 brd ff:ff:ff:ff:ff:ff
inet 195.2.3.180/24 brd 195.2.3.255 scope global eth0
....
10: tunl1@NONE: <POINTOPOINT,MULTICAST,NOARP,UP> mtu 1480 qdisc noqueue
link/ipip 195.2.3.180 peer 195.2.3.179
inet 195.2.3.180/32 scope link tunl1
# ip route
195.2.3.0/24 dev eth0 proto kernel scope link src 195.2.3.180
multicast 224.0.0.0/4 dev tunl1 scope link
default via 195.2.3.1 dev eth0
As a result, IGMP Join and Leave messages are sent in this form...
outer IP inner IP
Src Dst Src Dst
195.2.3.180 195.2.3.179 195.2.3.180 224.1.2.3
...while the rest of the traffic (I use vic for the test) looks like
this...
outer IP
Src Dst
195.2.3.180 224.1.2.3 <<< udp data >>>
...so, no tunnel at all.
If I modify the tunnel settings to (set the local address to
10.0.0.1)...
# ip addr
....
10: tunl1@NONE: <POINTOPOINT,MULTICAST,NOARP,UP> mtu 1480 qdisc noqueue
link/ipip 195.2.3.180 peer 195.2.3.179
inet 10.0.0.1/32 scope link tunl1
...then all my datagrams (IGMP and UDP as well) will go through the
tunnel...
outer IP inner IP
Src Dst Src Dst
195.2.3.180 195.2.3.179 10.0.0.1 224.1.2.3
...however, I am not satisfied with the inner source address, because
after decapsulation the datagram might not be correctly routed.
Then I modified the routing table (by specifying 195.2.3.180 as the
source address for the multicast traffic)...
# ip route
195.2.3.0/24 dev eth0 proto kernel scope link src 195.2.3.180
multicast 224.0.0.0/4 dev tunl1 scope link src 195.2.3.180
default via 195.2.3.1 dev eth0
...and I got a combination of the two results indicated before: IGMP go
through tunnel (entry point = 10.0.0.1), UDP are not tunneled at all.
IGMP:
outer IP inner IP
Src Dst Src Dst
195.2.3.180 195.2.3.179 10.0.0.1 224.1.2.3
UDP:
outer IP
Src Dst
195.2.3.180 224.1.2.3 <<< udp data >>>
...so, no tunnel at all.
So, where am I wrong ? Any help would be greatly appreciated.
Thank you,
John.
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