Please use the -n (numeric) option for iptables in order to prevent it from Timeouts may be _very_ long, depending on your ruleset. The problem is, if you use private IP addresses (like 10.x.x.x or .x),ĭNS is unable to resolve a hostname and times out. Rule consists out of two addresses, the worst case is two DNS lookups per This is because iptables does a DNS lookup for each IP address. 3.11 iptables -L takes a very long time to display the rules Please update to latest SVN or use iptables >= 1.2.1 as You can print the output of this file usingģ.9 How do I list all available IP tables?ģ.10 iptables-save / iptables-restore from iptables-1.2 segfaults There is a file in the proc-filesystem, which is called /proc/net/ip_conntrack. values of the power of two) are a bad choice.ģ.8 How do I list all tracked / masqueraded connections, similar to 'ipchains -L -M' in 2.2.x ? Please note that due to the nature of the current hashing algorithm, anĮven hash bucket count (and esp. The hashsize module loadtime parameter of the ip_conntrack.o To optimize performance, please also raise the number of hash buckets by using You can easily increase the number of maximal tracked connections, but beĪware that each tracked connection eats about 350 bytes of non-swappable This number is dependent on you system's maximum memory size (at 64MB: 4096, Tracking by default handles up to a certain number of simultaneous connections. If you notice the following message in syslog, it looks like the conntrackĭatabase doesn't have enough entries for your environment. 3.7 ip_conntrack: maximum limit of XXX entries exceeded With the same source port, netfilter would have to mangle IP and port ifīut if there are more than one available, it again only has to With local port 1234, the netfilter box only mangles the IP address andĪs soon as somebody else opens another connection Rebooted machine, and somebody behind the SNAT box opens a connection Netfilter tries to mangle as little as possible. 3.6 How does SNAT to multiple addresses work? If you just use firewalling without NAT it should work fine. 3.5 The IRC module is unable to handle DCC RESUME In current kernel there is no need to patch anything. So you want to build a completely transparent firewall? Great idea! 3.4 I'm unable to use netfilter in combination with the Linux bridging code In particular versions of the linux kernel (2.4.19=2.4.21-pre4) this message is no longer M are 1, and the message is followed by, reusing. This is normally nothing to worry about, especially if N and Ip_conntrack: max number of expected connections N of M reached for -> My sylog or console regularly shows messages like: 3.3 ip_conntrack: max number of expected connections N of M reached for -> Packets get dropped by the NAT code before they reach the filter Iptables -t mangle -A PREROUTING -j LOG -m state -state INVALIDĪnd yes, you have to put the rule in the mangle table, because the You suspect it are remote probe / scanning packets), use the following If you want to have a more detailed logging of these packets (i.e.
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