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Operating Systems Linux Red Hat Name resolution is only working from server side. Clients cannot resolve host names. Post 302729297 by dbadmin100 on Friday 9th of November 2012 12:06:45 PM
Old 11-09-2012
I had removed the bind packages by the time your message was posted. But this time I did not install the bind-chroot package and used the standard bind. However, I hit exactly the same issue. [can ping ip addresses in all directions but hostname ping only works from server]. So I checked the udp/tcp port 53 but did not find them in netstat -an. I issued the following commands as found in google and did /etc/init.d/iptables restart but no joy. So looks like this might be the issue why my clients cannot reach the dns server. Any ideas on how to open udp and tcp port 53 please (CentOS 5)?

Code:
iptables -A INPUT -p tcp -m tcp --sport 53 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT
iptables -A INPUT -p udp -m udp --sport 53 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT
iptables -A OUTPUT -p tcp -m tcp --sport 1024:65535 --dport 53 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -p udp -m udp --sport 1024:65535 --dport 53 -m state --state NEW,ESTABLISHED -j ACCEPT

 

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SS(8)							      System Manager's Manual							     SS(8)

NAME
ss - another utility to investigate sockets SYNOPSIS
ss [options] [ FILTER ] DESCRIPTION
ss is used to dump socket statistics. It allows showing information similar to netstat. It can display more TCP and state informations than other tools. OPTIONS
These programs follow the usual GNU command line syntax, with long options starting with two dashes (`-'). A summary of options is included below. -h, --help Show summary of options. -V, --version Output version information. -n, --numeric Do now try to resolve service names. -r, --resolve Try to resolve numeric address/ports. -a, --all Display all sockets. -l, --listening Display listening sockets. -o, --options Show timer information. -e, --extended Show detailed socket information -m, --memory Show socket memory usage. -p, --processes Show process using socket. -i, --info Show internal TCP information. -s, --summary Print summary statistics. This option does not parse socket lists obtaining summary from various sources. It is useful when amount of sockets is so huge that parsing /proc/net/tcp is painful. -4, --ipv4 Display only IP version 4 sockets (alias for -f inet). -6, --ipv6 Display only IP version 6 sockets (alias for -f inet6). -0, --packet Display PACKET sockets. -t, --tcp Display only TCP sockets. -u, --udp Display only UDP sockets. -d, --dccp Display only DCCP sockets. -w, --raw Display only RAW sockets. -x, --unix Display only Unix domain sockets. -f FAMILY, --family=FAMILY Display sockets of type FAMILY. Currently the following families are supported: unix, inet, inet6, link, netlink. -A QUERY, --query=QUERY List of socket tables to dump, separated by commas. The following identifiers are understood: all, inet, tcp, udp, raw, unix, packet, netlink, unix_dgram, unix_stream, packet_raw, packet_dgram. -D FILE Do not display anything, just dump raw information about TCP sockets to FILE after applying filters. If FILE is - stdout is used. -F FILE, --filter=FILE Read filter information from FILE. Each line of FILE is interpreted like single command line option. If FILE is - stdin is used. FILTER := [ state TCP-STATE ] [ EXPRESSION ] Please take a look at the official documentation (Debian package iproute-doc) for details regarding filters. USAGE EXAMPLES
ss -t -a Display all TCP sockets. ss -u -a Display all UDP sockets. ss -o state established '( dport = :ssh or sport = :ssh )' Display all established ssh connections. ss -x src /tmp/.X11-unix/* Find all local processes connected to X server. ss -o state fin-wait-1 '( sport = :http or sport = :https )' dst 193.233.7/24 List all the tcp sockets in state FIN-WAIT-1 for our apache to network 193.233.7/24 and look at their timers. SEE ALSO
ip(8), /usr/share/doc/iproute-doc/ss.html (package iproutedoc) AUTHOR
ss was written by Alexey Kuznetosv, <kuznet@ms2.inr.ac.ru>. This manual page was written by Michael Prokop <mika@grml.org> for the Debian project (but may be used by others). SS(8)
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