[fw-wiz] RE:[fw-wiz]: unable to ping behind the firewall
From: Sloane, David (DSloane_at_vfa.com)
To: "Hilal Hussein" <firstname.lastname@example.org>, <email@example.com> Date: Wed, 10 Dec 2003 11:17:03 -0500
It sounds like you have too many variables to make sense of the
I'm assuming there's some reason you can't find or clean the
virus-infected/bad-arp computer. If you can find it, at least pull it
off the network for a while for testing. If you can't find it because
it produces invalid Ethernet addresses, disconnect half of your
workstations and sniff for the ARP packets. Dividing the pool in half,
and half again, and so on, can make this a manageable process.
I would try to make sure that the network equipment is all working as
desired first. For example, if you put a
(hardened/firewalled/disposable/knoppix) computer on the same switch as
the firewall and the ISP router, give it a real IP address and try ping
and https. If that works, you've eliminated the switch and the ISP
router - they aren't causing the problem.
Then go back behind the firewall with a single workstation - maybe a
crossover cable from the firewall to a clean computer, and try ping and
https. If those work, your firewall is probably configured correctly
and you're back to finding the problem computer on the network. Maybe
your LAN switch is broken, but a Layer 2 switch is unlikely to fail for
some IP protocols and not others.
There are certainly other ways to do this, but this is how I would
[mailto:firstname.lastname@example.org] On Behalf Of Hilal
Sent: December 08, 2003 6:10 AM
Subject: [fw-wiz] [fw-wiz]: unable to ping behind the firewall
I have a problem, and would like to take your comment, feedback, and
guidelines about how to resolve it.
I have a network with the following setup : ISP router connected
a 3 com 16 port switch in our network, and this switch is connected
to a cisco pix firewall.
so, we are getting internet access throught the firewall then switch
isp router ...
from our network,we can browse the internet, telnet, msn, chating, but
CAN"T do ping any
nternet host (like yahoo, or cnn) and also some users can't access the
internet web based BANK LOGGIN ACCOUNT like https, and maybe other
notice that :
1 - All oubound tcp & udp ports including the 443/TCP (outbound) port
Open t on the firewall.
2 - Our internet PC's are mostly winxp professional, only few are
98, and all are security patchedand the IP addresses belong to the
3 - Our network has been infected and still infected by a virus that is
using one of the
pc's to generate lots of arp traffics which is affecting the whole
4 - my firewall is not blocking the icmp as:
- conduit permit icmp any any
- outbound permit x.x.x.x. x.x.x.x (internal network) icmp
i already consulted the ISP, they did not block the ICMP request/respond
packets. Even other customers connected to the same router of the ISP
able to do the ping but we can't.
also i am unable to even ping the ip address of the router of the ISP!
i would like to know if this is causing the unavailability of ping and
services? in other word, does flooding (if it is flooding) the arp table
the firewall wil cause this problem?
suppositely that it is not because of firewall, could it be because of
Moreover, I am using the Kiwi Syslog Daemon software to audit logs of
the pix firewall, but it is not giving anything on the screen as it is
saying "unable to open UDP socket on port 514". And i am running kiwi on
a winxp PC. Please tell me, is this issue related to the aboved
mentioned issue or what? if not, how to resolve it, knowing that i
installed Fport and it showed me that udp port is already used by the
sytem, with no service name mentioned.
I wish you are not confused with these junk of issues, maybe it is
related maybe not, but all i want to say that it happened all at once,
and i am not able to figure out what could be the resolution steps.
thanks for any future input, and i really appreciate comming out with a
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