[j-nsp] SRX Static NAT - Not working in both directions

Oliver Garraux oliver at g.garraux.net
Fri Sep 7 15:22:34 EDT 2012


I recently bought an SRX and have been trying the different NAT
configuration options to become more familar with JunOS.

Static NAT isn't operating quite as I'd expect from the documentation.
 My understanding is that static NAT should be bidirectional, in that
it should translate connections going in both directions.

I'm using on the interface connected to the rest of my
network (ge-0/0/0.100), and on vlan.200 on my SRX.
ge-0/0/0.100 is in the "trust" zone, and vlan.200 is in the "user"

static {
    rule-set user_to_trust {
        from zone trust;
        rule desktop1 {
            match {
            then {
                static-nat prefix;
proxy-arp {
    interface ge-0/0/0.100 {
        address {

I'm only seeing it translate connections coming in to the destination
address (  The source address on connections initiated
by the "static-nat" address ( - the address on the
desktop sitting behind my SRX) are not being translated to  Am I misunderstanding how static NAT works?

I've tried using an IP that is routed to the SRX (where no proxy-arp
should have been required in that situation).  I also don't see the
address being translated when I look at these flows in "show security
flow session", so I don't think this is an issue with proxy-arp.  I'm
permitting all traffic between the "user" and "trust" zones (in both
directions) in my security policies.

Here's one of the flow entries when I try to ping from

Session ID: 21626, Policy name: permit-all/5, Timeout: 16, Valid
  In: -->;icmp, If: vlan.200,
Pkts: 1, Bytes: 60
  Out: -->;icmp, If:
ge-0/0/0.100, Pkts: 0, Bytes: 0

Any ideas?




Oliver Garraux
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