Dos IPs de la misma subnet (Policy Base Routing)
Paremetros del kernel
sysctl -w net.ipv4.conf.all.arp_ignore=2
sysctl -w net.ipv4.conf.default.arp_ignore=2
sysctl -w net.ipv4.conf.all.arp_announce=2
sysctl -w net.ipv4.conf.default.arp_announce=2
sysctl -w net.ipv4.conf.all.arp_filter=1
sysctl -w net.ipv4.conf.default.arp_filter=1
arp_filter - BOOLEAN :
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.
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.
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}