Hi. I got similar problems after I moved to 2.6.17.6 from 2.6.14 I've downloaded latest POM and patched kernel manually I didn't notice if there were any warnings when building kernel. Iptables version is 1.3.5, built against 2.5.17.6 kernel This is what I get when I try to use connlimit match m64:~# iptables -A INPUT -p tcp --dport 80 -m connlimit --connlimit-above 10 -j REJECT iptables: Unknown error 18446744073709551615 m64:~# iptables -I INPUT -p tcp --syn --dport 80 -j DROP -m connlimit --connlimit-above 10 iptables: Unknown error 18446744073709551615 Architecture is x86_64, actually amd64 here's a part of lsmod output: Module Size Used by xt_MARK 3456 0 xt_multiport 4288 0 ipt_connlimit 4032 0 ip_conntrack 68020 1 ipt_connlimit nfnetlink 9096 1 ip_conntrack xt_tcpudp 4352 0 iptable_filter 3840 0 ip_tables 23648 1 iptable_filter x_tables 20488 5 xt_MARK,xt_multiport,ipt_connlimit,xt_tcpudp,ip_tables ipv6 312128 28 Kernel config: # Core Netfilter Configuration # CONFIG_NETFILTER_NETLINK=m CONFIG_NETFILTER_NETLINK_QUEUE=m CONFIG_NETFILTER_NETLINK_LOG=m CONFIG_NETFILTER_XTABLES=m CONFIG_NETFILTER_XT_TARGET_CLASSIFY=m CONFIG_NETFILTER_XT_TARGET_CONNMARK=m CONFIG_NETFILTER_XT_TARGET_MARK=m CONFIG_NETFILTER_XT_TARGET_NFQUEUE=m CONFIG_NETFILTER_XT_TARGET_NOTRACK=m CONFIG_NETFILTER_XT_MATCH_COMMENT=m CONFIG_NETFILTER_XT_MATCH_CONNBYTES=m CONFIG_NETFILTER_XT_MATCH_CONNMARK=m CONFIG_NETFILTER_XT_MATCH_CONNTRACK=m CONFIG_NETFILTER_XT_MATCH_DCCP=m CONFIG_NETFILTER_XT_MATCH_ESP=m CONFIG_NETFILTER_XT_MATCH_HELPER=m CONFIG_NETFILTER_XT_MATCH_LENGTH=m CONFIG_NETFILTER_XT_MATCH_LIMIT=m CONFIG_NETFILTER_XT_MATCH_MAC=m CONFIG_NETFILTER_XT_MATCH_MARK=m CONFIG_NETFILTER_XT_MATCH_POLICY=m CONFIG_NETFILTER_XT_MATCH_MULTIPORT=m CONFIG_NETFILTER_XT_MATCH_PHYSDEV=m CONFIG_NETFILTER_XT_MATCH_PKTTYPE=m CONFIG_NETFILTER_XT_MATCH_REALM=m CONFIG_NETFILTER_XT_MATCH_SCTP=m CONFIG_NETFILTER_XT_MATCH_STATE=m CONFIG_NETFILTER_XT_MATCH_STRING=m CONFIG_NETFILTER_XT_MATCH_TCPMSS=m # # IP: Netfilter Configuration # CONFIG_IP_NF_CONNTRACK=m CONFIG_IP_NF_CT_ACCT=y CONFIG_IP_NF_CONNTRACK_MARK=y CONFIG_IP_NF_CONNTRACK_EVENTS=y CONFIG_IP_NF_CONNTRACK_NETLINK=m CONFIG_IP_NF_CT_PROTO_SCTP=m CONFIG_IP_NF_FTP=m CONFIG_IP_NF_IRC=m CONFIG_IP_NF_NETBIOS_NS=m CONFIG_IP_NF_TFTP=m CONFIG_IP_NF_AMANDA=m CONFIG_IP_NF_PPTP=m CONFIG_IP_NF_H323=m CONFIG_IP_NF_QUEUE=m CONFIG_IP_NF_IPTABLES=m CONFIG_IP_NF_MATCH_IPRANGE=m CONFIG_IP_NF_MATCH_TOS=m CONFIG_IP_NF_MATCH_RECENT=m CONFIG_IP_NF_MATCH_ECN=m CONFIG_IP_NF_MATCH_DSCP=m CONFIG_IP_NF_MATCH_AH=m CONFIG_IP_NF_MATCH_TTL=m CONFIG_IP_NF_MATCH_OWNER=m CONFIG_IP_NF_MATCH_ADDRTYPE=m CONFIG_IP_NF_MATCH_HASHLIMIT=m CONFIG_IP_NF_FILTER=m CONFIG_IP_NF_TARGET_REJECT=m CONFIG_IP_NF_TARGET_LOG=m CONFIG_IP_NF_TARGET_ULOG=m CONFIG_IP_NF_TARGET_TCPMSS=m CONFIG_IP_NF_NAT=m CONFIG_IP_NF_NAT_NEEDED=y CONFIG_IP_NF_TARGET_MASQUERADE=m CONFIG_IP_NF_TARGET_REDIRECT=m CONFIG_IP_NF_TARGET_NETMAP=m CONFIG_IP_NF_TARGET_SAME=m CONFIG_IP_NF_NAT_SNMP_BASIC=m CONFIG_IP_NF_NAT_IRC=m CONFIG_IP_NF_NAT_FTP=m CONFIG_IP_NF_NAT_TFTP=m CONFIG_IP_NF_NAT_AMANDA=m CONFIG_IP_NF_NAT_PPTP=m CONFIG_IP_NF_NAT_H323=m CONFIG_IP_NF_MANGLE=m CONFIG_IP_NF_TARGET_TOS=m CONFIG_IP_NF_TARGET_ECN=m CONFIG_IP_NF_TARGET_DSCP=m CONFIG_IP_NF_TARGET_TTL=m CONFIG_IP_NF_TARGET_CLUSTERIP=m CONFIG_IP_NF_RAW=m CONFIG_IP_NF_ARPTABLES=m CONFIG_IP_NF_ARPFILTER=m CONFIG_IP_NF_ARP_MANGLE=m CONFIG_IP_NF_MATCH_CONNLIMIT=m and, finally dmesg tells me: ip_tables: connlimit match: invalid size 0 != 24 ip_tables: connlimit match: invalid size 0 != 24 Thank you. Adlan