Screen OS

I have a *PUBLIC* /26 IP address range which I am sub-dividing into /30, /30, /28, and /28 networks.

The network diagram is a follows:

ISP Router --(/30)--> Our Router --(/30)--> SSG-5 --(/28)--> DMZ

                                                                                 |-------(/28)-->Trusted

The problem is that I cannot ping the inside interface of the router from the DMZ or Trusted zone (actually I can ping the router, and I see that the router receives the packets form its packet count, but they fail to route on return to the firewall).  However, If the zones/interfaces are set to use NAT, I can ping router.  Correct me if I am wrong but I should NOT have to use NAT, I am using all static routes and public IP address space.

Any help would be greatly appreciated.

Here is my configuration:

unset key protection enable
set clock timezone 0
set vrouter trust-vr sharable
set vrouter "untrust-vr"
exit
set vrouter "trust-vr"
unset auto-route-export
exit
set alg appleichat enable
unset alg appleichat re-assembly enable
set alg sctp enable
set auth-server "Local" id 0
set auth-server "Local" server-name "Local"
set auth default auth server "Local"
set auth radius accounting port 1646
set admin auth web timeout 10
set admin auth dial-in timeout 3
set admin auth server "Local"
set admin format dos
set zone "Trust" vrouter "trust-vr"
set zone "Untrust" vrouter "trust-vr"
set zone "DMZ" vrouter "trust-vr"
set zone "VLAN" vrouter "trust-vr"
set zone "Untrust-Tun" vrouter "trust-vr"
set zone "Trust" tcp-rst
set zone "Untrust" block
unset zone "Untrust" tcp-rst
set zone "MGT" block
unset zone "V1-Trust" tcp-rst
unset zone "V1-Untrust" tcp-rst
set zone "DMZ" tcp-rst
unset zone "V1-DMZ" tcp-rst
unset zone "VLAN" tcp-rst
set zone "Untrust" screen tear-drop
set zone "Untrust" screen syn-flood
set zone "Untrust" screen ping-death
set zone "Untrust" screen ip-filter-src
set zone "Untrust" screen land
set zone "V1-Untrust" screen tear-drop
set zone "V1-Untrust" screen syn-flood
set zone "V1-Untrust" screen ping-death
set zone "V1-Untrust" screen ip-filter-src
set zone "V1-Untrust" screen land
set interface "ethernet0/0" zone "Untrust"
set interface "ethernet0/1" zone "DMZ"
set interface "bgroup0" zone "Trust"
set interface bgroup0 port ethernet0/2
set interface bgroup0 port ethernet0/3
set interface bgroup0 port ethernet0/4
set interface bgroup0 port ethernet0/5
set interface bgroup0 port ethernet0/6
unset interface vlan1 ip
set interface ethernet0/0 ip x.y.71.6/30
set interface ethernet0/0 route
set interface ethernet0/1 ip x.y.71.17/28
set interface ethernet0/1 route
set interface bgroup0 ip x.y.71.49/28
set interface bgroup0 route
set interface ethernet0/0 gateway x.y.71.5
set interface ethernet0/0 gateway x.y.71.5
set interface ethernet0/0 gateway x.y.71.5
unset interface vlan1 bypass-others-ipsec
unset interface vlan1 bypass-non-ip
set interface ethernet0/0 ip manageable
set interface ethernet0/1 ip manageable
set interface bgroup0 ip manageable
set interface bgroup0 manage mtrace
set interface "serial0/0" modem settings "USR" init "AT&F"
set interface "serial0/0" modem settings "USR" active
set interface "serial0/0" modem speed 115200
set interface "serial0/0" modem retry 3
set interface "serial0/0" modem interval 10
set interface "serial0/0" modem idle-time 10
set flow tcp-mss
unset flow tcp-syn-check
unset flow tcp-syn-bit-check
set flow reverse-route clear-text prefer
set flow reverse-route tunnel always
set pki authority default scep mode "auto"
set pki x509 default cert-path partial
set crypto-policy
exit
set ike respond-bad-spi 1
set ike ikev2 ike-sa-soft-lifetime 60
unset ike ikeid-enumeration
unset ike dos-protection
unset ipsec access-session enable
set ipsec access-session maximum 5000
set ipsec access-session upper-threshold 0
set ipsec access-session lower-threshold 0
set ipsec access-session dead-p2-sa-timeout 0
unset ipsec access-session log-error
unset ipsec access-session info-exch-connected
unset ipsec access-session use-error-log
set vrouter "untrust-vr"
exit
set vrouter "trust-vr"
exit
set url protocol websense
exit
set policy id 1 from "Trust" to "Untrust"  "Any" "Any" "ANY" permit
set policy id 1
exit
set nsmgmt bulkcli reboot-timeout 60
set ssh version v2
set config lock timeout 5
unset license-key auto-update
set telnet client enable
set snmp port listen 161
set snmp port trap 162
set vrouter "untrust-vr"
exit
set vrouter "trust-vr"
unset add-default-route
exit
set vrouter "untrust-vr"
exit
set vrouter "trust-vr"
exit

You don't appear to have any policies to allow inter-zone traffic except from trust to untrust. So pings to/from trust to dmz will fail (Assuming I read your question correctly) without a policy.

---

@muttbarker wrote:

You don't appear to have any policies to allow inter-zone traffic except from trust to untrust. So pings to/from trust to dmz will fail (Assuming I read your question correctly) without a policy.

---

I am pinging from the Trust to the Router, (Trust -> Untrust -> Router, then the Router responds to the Untrust, which at this point it is lost / dropped).

My configuration has an ANY ANY permit policy from Trust to Untrust (as shown above).

I hope this clears it up.  For what its worth, I still added any any permit policies to DMZ to Trust, DMZ to untrust, and still the ping fails.

I appreciate the help though!

Looking at your config - you are trying to ping to 71.5 from 71.49 and the return fails - well one question I would have - do you have a route back to 71.49 specified on the 71.5. device? 

Because looking at your config a ping from the trust zone to 71.5 is going to work fine from the SSG5 point of view. So the problem is not there. You could verify that with debug.

When you use NAT the ping is sourced as coming from 71.6 so there is no issue with the return route. Not true when coming from 71.49. Make sense?

---

@muttbarker wrote:

Looking at your config - you are trying to ping to 71.5 from 71.49 and the return fails - well one question I would have - do you have a route back to 71.49 specified on the 71.5. device? 

 

Because looking at your config a ping from the trust zone to 71.5 is going to work fine from the SSG5 point of view. So the problem is not there. You could verify that with debug.

 

When you use NAT the ping is sourced as coming from 71.6 so there is no issue with the return route. Not true when coming from 71.49. Make sense?

 

---

Thank you for the explanation as to why the NAT worked and not the static routing, makes perfect sense.  I do have routes on the 71.5 Router, but it looks like I will have to revisit them; the problem is most likely there.  Debug did not show any traffic from the 71.5 src-ip. Thanks, you have been a big help.

Hi!

Please ask your ISP if the router contains a static route for the  /26-network that points to the SSG5 untrust IP.

The router is responding requests coming from its connected /30-network but does not know how to reach the rest of the /26-network.

Kind regards,

Edouard