Running NAT and can't Ping

Shu Bin Zhu shubinzhu at
Sun Sep 26 07:42:08 PDT 2004

I have a strange problem.  Here is my setup.
ISP 1                    ISP 2
  |                            |
Router 1                Router 2           Internet Address A
  |                            |
  |                            |
  ----------------------  Switch --------------------       
  |                            |                        |
FreeBSD1         FreeBSD2               Windows 2000   
                        Internet Address B
The problem is if NAT on FreeBSD2 is not running, all the machines can ping each other.
If FreeBSD2 runs NAT, ping still works, except FreeBSD2 can't ping Router1 ( and FreeBSD1 ( FreeBSD2 can ping to the interent fine.
The Windows 2000 machines gets it's IP from DHCP running on FreeBSD2.  For a day, FreeBSD can't ping Windows 2000 either.  But now it is able to.
The NAT configuration on FreeBSD2 is :
/sbin/natd -u -a ( Internet Address B)
/sbin/ipfw -f flush
/sbin/ipfw add divert natd all from any to any via ( Internet Address B)
/sbin/ipfw add pass all from any to any

The unusual setup is the FreeBSD2 only has one ethernet card, and is doing IP aliasing.
I have another setup with 2 FreeBSD boxes, and one or both of them are doing NAT, and doesn't have this 'one way' ping problem.
Thanks in advance.

Do you Yahoo!?
Yahoo! Mail Address AutoComplete - You start. We finish.

More information about the freebsd-questions mailing list