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Full Discussion: IP Traffic forwarding
Operating Systems Linux IP Traffic forwarding Post 302344622 by Anuradhai4i on Monday 17th of August 2009 07:01:48 AM
Old 08-17-2009
Bug IP Traffic forwarding

Hello All

I have the following setup of a network. Client machines sends requests to the server which is (192.168.1.50) running on Ubuntu server 8.04. And this server forwards all incoming traffic from clients to another server (192.168.1.100) when it's available. The availability is checked periodically using a shell script.

The following NAT rule has been given for the forwarding task.
Rule 1: Iptables -t nat -A PREROUTING -d 192.168.1.50 -j DNAT --to-destination 192.168.1.100

In the event 192.168.1.100 is unavailable the shell script will detect the unavailability and shift the traffic to 192.168.1.200. The current iptable rules are flushed and the following rule is applied.

Rule 2: Iptables -t nat -A PREROUTING -d 192.168.1.50 -j DNAT --to-destination 192.168.1.200

In the normal scenario when 192.168.1.100 is available the forwarding rule (Rule 1) works properly. The issue is when 192.168.1.100 is unavailable and the traffic is shifted to 192.168.1.200 the traffic is not forwarded properly as required. However when 192.168.1.50 is rebooted and Rule 2 is applied the
forwarding happened as required.

ARP cache and router cache was cleared as well but that did not
solve the issue. The issue was solved only after rebooting 192.168.1.50

Any idea that I can get this sone without rebooting 192.168.1.50 ?

Thank you in advance
Anuradha Smilie
 

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IFNDP-PROXY(5)						       Network configuration						    IFNDP-PROXY(5)

NAME
ifndp-proxy[-<interface name>] - IPv6 NDP and IPv4 ARP proxy entries SYNOPSIS
/etc/sysconfig/network/ifndp-proxy /etc/sysconfig/network/ifndp-proxy-<interface name> DESCRIPTION
These files contain IPv6 NDP and IPv4 ARP proxy settings, that should be applied using the ip neigh add proxy command documented in the ip(8) manual page that provides a common interface for IPv4 and IPv6. The NDP/ARP proxy is required, e.g. when IP addresses from the same subnet have to be used on the interface of the host as well as on interfaces behind a (tunnel) interface and using a bridge is not an option. Don't forget to enable forwarding and the NDP/ARP proxy by setting net.ipv6.conf.<all|default|interface name>.proxy_ndp = 1 net.ipv6.conf.<all|default|interface name>.forwarding = 1 and/or net.ipv4.conf.<all|default|interface name>.proxy_arp = 1 net.ipv4.conf.<all|default|interface name>.forwarding = 1 or net.ipv4.ip_forward = 1 either as global all setting in the /etc/sysctl.conf file or using the ifsysctl(5) files, that allow per-interface setup. Forwarding can be also enabled in the /etc/sysconfig/sysctl file using the IP_FORWARD and IPV6_FORWARD variables. The proxy entries are added and deleted using the if-{up|down}.d/ndp-proxy script, every time after an involved interface has been set up or down. SYNTAX
The format of the ifndp-proxy file is: <address> <address interface> <proxy interface list> The format of the ifndp-proxy-<address interface> file is same to above, but allows also to omit the address interface by using a "-" as placeholder inside of the file, because it is already available in the file name: <address> <address interface | -> <proxy interface list> Lines beginning with # and blank lines are ignored. Each line defines to add a proxy NDP/ARP entry with the address of or behind address interface to all interfaces in the proxy interface list. EXAMPLES
Let's assume, your machine is connected via eth0 to a switch with the networks 2001:db8:abba::/64 and 192.168.100.1/24 and is using the IP address 1 itself. You'd like to use the addresses 11 and 12 e.g. for virtual machines behind the tap1 and tap2 interface, that is: 2001:db8:abba::1/64 -- local eth0 address 2001:db8:abba::11/64 -- address behind tap1 2001:db8:abba::12/64 -- address behind tap2 192.168.100.1/24 -- local eth0 address 192.168.100.11/24 -- address behind tap1 192.168.100.12/24 -- address behind tap2 then set up the following entries in the ifndp-proxy file: 2001:db8:abba::1 eth0 tap1 tap2 2001:db8:abba::11 tap1 eth0 tap2 2001:db8:abba::12 tap2 eth0 tap1 192.168.100.1 eth0 tap1 tap2 192.168.100.11 tap1 eth0 tap2 192.168.100.12 tap2 eth0 tap1 additionally to the routing entries in the routes or ifroute-<interface name> files. BUGS
Please report bugs at <https://bugzilla.novell.com/> AUTHOR
Marius Tomaschewski <mt@suse.de> SEE ALSO
ifup(8) ifcfg(5) ifsysctl(8) sysconfig December 2009 IFNDP-PROXY(5)
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