topic Re: port 80 open or filtered in Operating System - Linux

port 80 open or filtered

skt_skt — Thu, 24 Apr 2008 17:28:35 GMT

case1

#nmap -v -p 80 rhnserver

Port State Service
80/tcp open http

case2

#nmap -v -p 80 rhnserver

Port State Service
80/tcp filtered http

i have couple of servers showing similar symptoms.. some of them are able to talk to the rhn server on port 80 and some of them not.

Could some guide me here. AFAIK, there is know config diffrence among them.

Re: port 80 open or filtered

Ivan Ferreira — Thu, 24 Apr 2008 19:13:59 GMT

"filtered" means that a SYN probe resulted
in neither a SYN-ACK nor a RST.

Sending a SYN probe to a port which wasn't filtered and on which no process was listening would result in a RST.

Sending a SYN probe which gets blocked by the filtering rules will produce the same result (e.g. no response, ICMP destination
unreachable) regardless of whether or not anything is listening on that port.

Re: port 80 open or filtered

skt_skt — Fri, 25 Apr 2008 09:01:12 GMT

2.4.21-47.ELsmp/Red Hat Enterprise Linux AS release 3 (Taroon Update 8)

I dont have any server level firewall seting like iptables. But neither any firwall rule is created at network level.

# cat /etc/services|grep 80
http 80/tcp www www-http # WorldWideWeb HTTP
http 80/udp www www-http # HyperText Transfer Protocol

Here is the oipen ports reported

Port State Service
21/tcp open ftp
22/tcp open ssh
111/tcp open sunrpc
135/tcp open loc-srv
381/tcp open hp-collector
383/tcp open hp-alarm-mgr
514/tcp open shell
1014/tcp open unknown
6001/tcp open X11:1
10000/tcp open snet-sensor-mgmt
13722/tcp open VeritasNetbackup
13782/tcp open VeritasNetbackup
13783/tcp open VeritasNetbackup
Remote operating system guess: Linux Kernel 2.4.0 - 2.5.20 w/o tcp_timestamps

Nmap run completed -- 1 IP address (1 host up) scanned in 5 seconds

Re: port 80 open or filtered

Jeeshan — Fri, 25 Apr 2008 16:29:51 GMT

Hi Santosh

Did you check the netstat command

#netstat -an|grep 80