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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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SHOREWALL-EXCLUSION(5)						  [FIXME: manual]					    SHOREWALL-EXCLUSION(5)

NAME
exclusion - Exclude a set of hosts from a definition in a shorewall configuration file. SYNOPSIS
!address-or-range[,address-or-range]... !zone-name[,zone-name]... DESCRIPTION
The first form of exclusion is used when you wish to exclude one or more addresses from a definition. An exclaimation point is followed by a comma-separated list of addresses. The addresses may be single host addresses (e.g., 192.168.1.4) or they may be network addresses in CIDR format (e.g., 192.168.1.0/24). If your kernel and iptables include iprange support, you may also specify ranges of ip addresses of the form lowaddress-highaddress No embedded whitespace is allowed. Exclusion can appear after a list of addresses and/or address ranges. In that case, the final list of address is formed by taking the first list and then removing the addresses defined in the exclusion. Beginning in Shorewall 4.4.13, the second form of exclusion is allowed after all and any in the SOURCE and DEST columns of /etc/shorewall/rules. It allows you to omit arbitrary zones from the list generated by those key words. Warning If you omit a sub-zone and there is an explicit or explicit CONTINUE policy, a connection to/from that zone can still be matched by the rule generated for a parent zone. For example: /etc/shorewall/zones: #ZONE TYPE z1 ip z2:z1 ip ... /etc/shorewall/policy: #SOURCE DEST POLICY z1 net CONTINUE z2 net REJECT /etc/shorewall/rules: #ACTION SOURCE DEST PROTO DEST # PORT(S) ACCEPT all!z2 net tcp 22 In this case, SSH connections from z2 to net will be accepted by the generated z1 to net ACCEPT rule. In most contexts, ipset names can be used as an address-or-range. Beginning with Shorewall 4.4.14, ipset lists enclosed in +[...] may also be included (see shorewall-ipsets[1] (5)). The semantics of these lists when used in an exclusion are as follows: o !+[set1,set2,...setN] produces a packet match if the packet does not match at least one of the sets. In other words, it is like NOT match set1 OR NOT match set2 ... OR NOT match setN. o +[!set1,!set2,...!setN] produces a packet match if the packet does not match any of the sets. In other words, it is like NOT match set1 AND NOT match set2 ... AND NOT match setN. EXAMPLES
Example 1 - All IPv4 addresses except 192.168.3.4 !192.168.3.4 Example 2 - All IPv4 addresses except the network 192.168.1.0/24 and the host 10.2.3.4 !192.168.1.0/24,10.1.3.4 Example 3 - All IPv4 addresses except the range 192.168.1.3-192.168.1.12 and the network 10.0.0.0/8 !192.168.1.3-192.168.1.12,10.0.0.0/8 Example 4 - The network 192.168.1.0/24 except hosts 192.168.1.3 and 192.168.1.9 192.168.1.0/24!192.168.1.3,192.168.1.9 Example 5 - All parent zones except loc any!loc FILES
/etc/shorewall/hosts /etc/shorewall/masq /etc/shorewall/rules /etc/shorewall/tcrules SEE ALSO
shorewall(8), shorewall-accounting(5), shorewall-actions(5), shorewall-blacklist(5), shorewall-hosts(5), shorewall_interfaces(5), shorewall-ipsets(5), shorewall-maclist(5), shorewall-masq(5), shorewall-nat(5), shorewall-netmap(5), shorewall-params(5), shorewall-policy(5), shorewall-providers(5), shorewall-proxyarp(5), shorewall-rtrules(5), shorewall-routestopped(5), shorewall-rules(5), shorewall.conf(5), shorewall-secmarks(5), shorewall-tcclasses(5), shorewall-tcdevices(5), shorewall-tcrules(5), shorewall-tos(5), shorewall-tunnels(5), shorewall-zones(5) NOTES
1. shorewall-ipsets http://www.shorewall.net/manpages/shorewall-ipsets.html [FIXME: source] 06/28/2012 SHOREWALL-EXCLUSION(5)
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