目前，我有以下 eth5 来接收 239.1.1.31 的多播数据。它有效。
$ ifconfig
eth5 Link encap:Ethernet HWaddr E4:11:5B:94:E1:F3
inet addr:10.185.2.2 Bcast:10.185.2.31 Mask:255.255.255.224
...
路线：
$ sudo ip route add 10.0.8.0/24 via 10.185.2.14 dev eth5
$ sudo ip route add 224.0.0.0/4 dev eth5
$ route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.185.2.0 0.0.0.0 255.255.255.224 U 1 0 0 eth5
10.0.8.0 10.185.2.14 255.255.255.0 UG 0 0 0 eth5
224.0.0.0 0.0.0.0 240.0.0.0 U 0 0 0 eth5
结果：
$ iperf -s -u -B 239.1.1.31 -p 51000 -i 1
------------------------------------------------------------
Server listening on UDP port 51000
Binding to local address 239.1.1.31
Joining multicast group 239.1.1.31
Receiving 1470 byte datagrams
UDP buffer size: 224 KByte (default)
------------------------------------------------------------
[ 3] local 239.1.1.31 port 51000 connected with 10.0.8.50 port 53253
[ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
[ 3] 0.0- 1.0 sec 0.00 Bytes 0.00 bits/sec 0.000 ms 0/ 0 (-nan%)
[ 3] 1.0- 2.0 sec 16.0 Bytes 128 bits/sec 0.000 ms 268435481/268435482 (1e+02%)
[ 3] 2.0- 3.0 sec 0.00 Bytes 0.00 bits/sec 0.000 ms 0/ 0 (-nan%)
...
$ sudo tcpdump -i eth5 dst host 239.1.1.31
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth5, link-type EN10MB (Ethernet), capture size 65535 bytes
13:57:46.194477 IP 10.0.8.32.41686 > 239.1.1.31.pago-services1: UDP, length 512
13:57:46.348176 IP 10.0.10.32.53089 > 239.1.1.31.pago-services2: UDP, length 512
13:57:46.562028 IP 10.0.8.41.48791 > 239.1.1.31.60001: UDP, length 24
...
现在我又多了一个接口 eth4 来接收 239.1.1.201 的多播数据：
$ ifconfig
eth4 Link encap:Ethernet HWaddr E4:11:5B:94:E1:F2
inet addr:10.185.130.2 Bcast:10.185.130.31 Mask:255.255.255.224
以下命令失败。
$ sudo ip route add 10.0.8.0/24 via 10.185.130.14 dev eth4
RTNETLINK answers: File exists
$ sudo ip route add 224.0.0.0/4 dev eth4
RTNETLINK answers: File exists
我应该如何从两个接口接收多播数据？谢谢。