Linux多網卡同IP段解決

　　linux/Documentation/networking/ip-sysctl.txt ：

　　arp_filter - BOOLEAN

　　1 - Allows you to have multiple network interfaces on the same

　　subnet, and have the ARPs for each interface be answered

　　based on whether or not the kernel would route a packet from

　　the ARP'd IP out that interface (therefore you must use source

　　based routing for this to work). In other words it allows control

　　of which cards (usually 1) will respond to an arp request.

　　0 - (default) The kernel can respond to arp requests with addresses

　　from other interfaces. This may seem wrong but it usually makes

　　sense, because it increases the chance of successful communication.

　　IP addresses are owned by the complete host on Linux, not by

　　particular interfaces. Only for more complex setups like load-

　　balancing, does this behaviour cause problems.

　　arp_filter for the interface will be enabled if at least one of

　　conf/{all,interface}/arp_filter is set to TRUE,

　　it will be disabled otherwise

　　arp_announce - INTEGER

　　Define different restriction levels for announcing the local

　　source IP address from IP packets in ARP requests sent on

　　interface:

　　0 - (default) Use any local address, configured on any interface

　　1 - Try to avoid local addresses that are not in the target's

　　subnet for this interface. This mode is useful when target

　　hosts reachable via this interface require the source IP

　　address in ARP requests to be part of their logical network

　　configured on the receiving interface. When we generate the

　　request we will check all our subnets that include the

　　target IP and will preserve the source address if it is from

　　such subnet. If there is no such subnet we select source

　　address according to the rules for level 2.

　　2 - Always use the best local address for this target.

　　In this mode we ignore the source address in the IP packet

　　and try to select local address that we prefer for talks with

　　the target host. Such local address is selected by looking

　　for primary IP addresses on all our subnets on the outgoing

　　interface that include the target IP address. If no suitable

　　local address is found we select the first local address

　　we have on the outgoing interface or on all other interfaces,

　　with the hope we will receive reply for our request and

　　even sometimes no matter the source IP address we announce.

　　The max value from conf/{all,interface}/arp_announce is used.

　　Increasing the restriction level gives more chance for

　　receiving answer from the resolved target while decreasing

　　the level announces more valid sender's information.

　　arp_ignore - INTEGER

　　Define different modes for sending replies in response to

　　received ARP requests that resolve local target IP addresses:

　　0 - (default): reply for any local target IP address, configured

　　on any interface

　　1 - reply only if the target IP address is local address

　　configured on the incoming interface

　　2 - reply only if the target IP address is local address

　　configured on the incoming interface and both with the

　　sender's IP address are part from same subnet on this interface

　　3 - do not reply for local addresses configured with scope host,

　　only resolutions for global and link addresses are replied

　　4-7 - reserved

　　8 - do not reply for all local addresses

　　The max value from conf/{all,interface}/arp_ignore is used

　　when ARP request is received on the {interface}

　　解決

　　echo 2 > /proc/sys/net/ipv4/conf/all/arp_announce

　　echo 1 > /proc/sys/net/ipv4/conf/all/arp_ignore

　　or

　　echo 1 > /proc/sys/net/ipv4/conf/all/arp_filter