Can Windows Firewall affect LAN traffic ?

[Stephen Ford]

2-PC LAN + network printer + router

Win XP Pro SP3

Can Windows Firewall affect / stop LAN traffic? The following problem often
raises questions about the firewall and I want to understand its relevance.
Discussions seems to get very convoluted and end up down blind alleys.

I contend that Windows Firewall (WF) only affects WAN traffic but I suspect
that just by replacing router#1 with router#2, this does not result in the
WF stopping PC-PC ping traffic. Is that right?



I am trying to replace a router with a new one. With router #1 in place Ping
between the PCs works fine. With router#2 in place all network traffic is
fine (eg PC-printer, PC-router & PC-Internet) apart from Ping PC-PC.

I have been through the usual issues of network configuration issues
ad-nausium includin IP addresses, DNS, sub-net mask etc. In deed if there
was a problem, then nothing would work with router#1 in place. But with
router#1 in place all network comms is fine. Put router#2 in place and all
network traffic is fine apart from ping PC-PC.

 

[Jack [MVP-Networking]]

Hi
The Router's NAT firewall affect only Traffic coming in from the Internet.
The Router is a combo unit of Routing Circuit, and a switch in the same box.
LAN traffic is only using the switch.
The difference that you experience could be a result of different setting
other Router's DHCP (Computers' IP assignment).
There are differences between Routers in the way they handle the IP
assignment. Some Routers keep the same IPs according the computer MAC
number.
Others can assigned it in up hazard manner (I.e. giving different IP number
to the same computer each time it starts.
The latter can confuse the LAN Traffic. The best is to use a Router that can
do Static DHCP. I.e the computer's TCP/IP can be set-to Auto Obtain and they
always would get the same IP.
Jack (MS, MVP-Networking).

 

[Stephen Ford]

I have established that both routers assign the same IP addresses. Maybe
therefore this is perhaps not an issue?

I have confirmed that with router#1 both PCs can ping the other, the printer
and router.

Further tests have shown that with router#2, PC#2 can ping PC#1 but PC#1
cannot ping PC#2.

Ping <PC name> is translated into the correct IP address on both PCs even
though on PC#1> ping PC#2 times out.

So PC#1 seems dodgy... ?

Curiouser and curiouser...

 

[smlunatick]

I have established that both routers assign the same IP addresses. Maybe
therefore this is perhaps not an issue?

I have confirmed that with router#1 both PCs can ping the other, the printer
and router.

Further tests have shown that with router#2, PC#2 can ping PC#1 but PC#1
cannot ping PC#2.

Ping <PC name> is translated into the correct IP address on both PCs even
though on PC#1> ping PC#2 times out.

So PC#1 seems dodgy... ?

Curiouser and curiouser...

Are you attempting to replace router1 with router 2 or adding router2?

How do these two PCs connect to the "routers?" Several newer wireless
routers tend to have a default option turned on which "prevents"
wireless "connected" PCs from viewing other PCs, either wired or
wireless. Several routers have this option known as "WLAN
Protection..."

 

[Stephen Ford]

Are you attempting to replace router1 with router 2 or adding router2?
Replace.

How do these two PCs connect to the router?
Wired. I want to limit the changes to one (new router only, not new router
and change to wireless).

It's odd that by using a different router one PC should fail to ping the
other PC but allow ping the other way.

 

[smlunatick]

Are you attempting to replace router1 with router 2 or adding router2?
Replace.

How do these two PCs connect to the router?
Wired. I want to limit the changes to one (new router only, not new router
and change to wireless).

It's odd that by using a different router one PC should fail to ping the
other PC but allow ping the other way.

What type of Internet security software?

Are both PCs part of the same Windows "workgroup?"

What versions / service pack level are on each?

 

[Stephen Ford]

What type of Internet security software?
McAfee

Are both PCs part of the same Windows "workgroup?"
Yes. As mentioned, if the old router is put back in place everything works
again, so the whole setup is correctly configured - well I assume it is
because it works ie PC-PC comms, PC-router comms, PC-internet access.

I have a feeling my desktop PC may be corrupt. I deleted any log files
recently that appeared below C:\ and then NTbackup stopped working.
Otherwise the PC seems to behave. I did this before trying the wireless
router, so I can't confirm whether the PC worked with the new router in
place or not. So there is something wierd going on between the PCs and the
PC & router.

What versions / service pack level are on each?--
Regards
Stephen Ford

 

[smlunatick]

What type of Internet security software?
McAfee

Are both PCs part of the same Windows "workgroup?"
Yes. As mentioned, if the old router is put back in place everything works
again, so the whole setup is correctly configured - well I assume it is
because it works ie PC-PC comms, PC-router comms, PC-internet access.

I have a feeling my desktop PC may be corrupt. I deleted any log files
recently that appeared below C:\ and then NTbackup stopped working.
Otherwise the PC seems to behave. I did this before trying the wireless
router, so I can't confirm whether the PC worked with the new router in
place or not. So there is something wierd going on between the PCs and the
PC & router.

What versions / service pack level are on each?> > >> Win XP Pro SP3

I have had "bad" experience with an Internet security "all in one"
software suite. I could access the Internet, ping all my network
printers and other PC. However, it blocked the network file sharing.
Then, that "on-line" support agent "scrapped" my PC. Then only thing
I could suggest is to uninstall McAfee and clear out all possible left-
over settings. Then, start from 'scratch" setting up you new router
and network.