Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 335
  • Last Modified:

NAT is the problem ?

I have the following configuration:

ADSL-----RouterVPN (172.25.6.1)------SWITCH------(172.25.6.254) PIX501 (192.168.1.254)--------PcA (192.168.1.100)
                                                             |
                                                             |
                                                    PcB (172.25.6.3)

All subnet masks are 24 bits.
RouterVPN has proper configuration.


I need PcA to be able to go outside and to be reachable from outside, hence i decided a static NAT by entering:

static (inside,outside) 172.25.6.205 192.168.1.100 netmask 255.255.255.255

Also I set the following default gateways:
For PcA: 192.168.1.254
For PcB: 172.25.6.1
For PIX: 172.25.6.1

After setting all the IP I performed some connectivity tests and got what follows:

From PcB:
ping 172.25.6.1 : OK
ping 172.25.6.254 : OK
ping 172.25.6.205 : NO RESPONSE

From PcA:
ping 192.168.1.254 : OK
ping 172.25.6.1 : NO RESPONSE

From PIX:
ping outside 172.25.6.1 : OK
ping outside 172.25.6.3 : ? I need to verify
ping inside 192.168.1.100 : OK


My questions are:
1)Is it enough to use only the "static (...,..)..."  command or should I use it after entering:
nat (inside) 1 192.168.1.100 netmask 255.255.255.255
global (outside) 1 172.25.6.205 netmask 255.255.255.255

2)Why can't I reach from PcA the router 172.25.6.1 ?

Thx in advance


0
minicuc
Asked:
minicuc
  • 3
  • 2
  • 2
  • +2
1 Solution
 
JFrederick29Commented:
Are you allowing ICMP traffic on the PIX outside interface?  If ICMP is not permitted, you won't be able to ping anything beyond the PIX from PcA or ping through the PIX from the outside interface.
0
 
gjohnson99Commented:
can you ping the internet form your  pix  ?

if you can the its not routing the segment 192.168.1.xx
0
 
Felix2000Commented:
Doing the static is fine but you also need to make an access list to allow traffic in. Otherwise the traffic is still denied.
Statics only make the translation for traffic allowed in.

This is an example access access list to allow traffic in from your natted ip and icmp

### Permit Access from anybody to host 172.25.6.25
access-list acloutin permit ip any 172.25.6.205

### If you want specific access you can do something like this for a website
# access-list acloutin permit tcp any 172.25.6.205 eq 80

### Permit Things like Ping / Traceroute through the pix
access-list acloutin permit icmp any interface outside unreachable
access-list acloutin permit icmp any interface outside time-exceeded
access-list acloutin permit icmp any interface outside echo-reply
access-list acloutin permit icmp any interface outside echo

### Apply the access list to the interface
access-group acloutin in interface outside

Hope that helps.

-= Felix =-
0
NFR key for Veeam Agent for Linux

Veeam is happy to provide a free NFR license for one year.  It allows for the non‑production use and valid for five workstations and two servers. Veeam Agent for Linux is a simple backup tool for your Linux installations, both on‑premises and in the public cloud.

 
NashvilleGuitarPickerCommented:
Your router can't connect to PC-A because the router doesn't know that 192.168.1.xx is handled by PIX501.  It assumes that the only addresses on its internal network are in the 172.25.6.0/??? subnet (whatever the netmask is), and that everything else must be on the external side.  If your RouterVPN supports it, you will need to add a route/gateway to 192.168.1.0/255.255.255.0 via 172.25.6.254.  Since 192.168.x.x addresses are technically considered "non-routable," this might present a problem.  Also, if your RouterVPN doesn't support static routes, you are in trouble.

Since RouterVPN does not know how to get to PC-A, it can not return the pings, even if your firewall rules are correct.  If you were to put a network sniffer (like Ethereal on a hub, not a switch) right in front of 172.25.6.1, then you should see the packets from PC-A, each one followed by "Destination Unreachable" packets from the router.

If that doesn't work, then one troubleshooting step is to try everything using routable addresses on PC-A and the PIX, and then change them to non-routable addresses once things are working, in case your router/PIX refuses to route the non-routable addresses.

- Will
0
 
Felix2000Commented:
RouterVPN or PC-B doesn't need routers for the 192.168.x.x it's being natted... to anyone infront of the nat he needs to try to connect to 172.25.6.205.

-= Felix =-
0
 
minicucAuthor Commented:
Thx all, i'll check and get back to you shortly
0
 
NashvilleGuitarPickerCommented:
Good point, Felix2000.  Somehow I must have been thinking that the NAT was on the other end.  In that case, disregard most of my previous post.
0
 
minicucAuthor Commented:
Felix  solution works fine.Thx.
Only couple of doubts:

1) It seems the ICMP access-list lines are not needed, PcA is able to ping RouterVPN even without them. Is it correct ?

2) Are these ICMP access-list lines equivalent to the following ICMp commands ?

icmp permit any echo-reply outside
icmp permit any echo outside
etc.

Thx
Roberto
0
 
Felix2000Commented:
I believe the ICMP lines are for the PIX itself  not things being or being NAT'ed by it.

PC A is allowed out since he is inside. The access lists should also help people coming from the outside to ping / traceroute to the router/nat ip's.
Traceroute's time-exceeded might not normally be allowed back through the pix by default.

Glad it helped
-= Felix =-
0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

  • 3
  • 2
  • 2
  • +2
Tackle projects and never again get stuck behind a technical roadblock.
Join Now