On Oct 4, 11:00*pm, "Stephen Ford"
wrote:
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...

"Jack [MVP-Networking]" wrote in message

...

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" wrote in message
...
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.

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..."