[j-nsp] NAT on SRX with routed IP range

Bill Blackford bblackford at gmail.com
Sat Feb 7 16:39:54 EST 2015


Be aware that a proxy-arp setting will get installed as a static discard. If you're redistributing statics, this may be a concern. I solved this by adding a term early I'm my export policy rejecting this prefix.

Sent from my iPhone

> On Feb 7, 2015, at 11:27, "Paul Stewart" <paul at paulstewart.org> wrote:
> 
> That's been my experience .... proxy arp only on the external.
> 
> Paul
> 
> 
> -----Original Message-----
> From: juniper-nsp [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of
> Jonathan Call
> Sent: Friday, February 6, 2015 3:00 PM
> To: Tyler Christiansen
> Cc: juniper-nsp at puck.nether.net
> Subject: Re: [j-nsp] NAT on SRX with routed IP range
> 
> I've been reading the Juniper documentation and confirmed that the proxy-arp
> statement is only needed when the  NAT IP falls within the subnet range of
> the external IP address of the egress interface. It will automatically
> proxy-arp for all else. It also doesn't matter if it is a source, a
> destination or a static NAT.
> In my case, the problem turned out to be a missing route on a third party
> device preventing the traffic from even reaching the SRX.
> Thanks!Date: Wed, 4 Feb 2015 14:16:02 -0800
> Subject: Re: [j-nsp] NAT on SRX with routed IP range
> From: tyler at adap.tv
> To: lordsith49 at hotmail.com
> CC: juniper-nsp at puck.nether.net
> 
> Nope.  It's been a while, but I just reviewed our configuration, we removed
> proxy-arp at some point.  Suppose it turns out proxy-arp wasn't needed.
> We also have security policy configuration like this:
>> show configuration security policies from-zone untrust to-zone trust 
>> policy <name> {
>    match {        source-address <Allowed external address>;
> destination-address <internal RFC1918 IP>;        application [ <list of
> ports/applications> ];    }    then {        permit;    }}
> If you want to make the NAT work for any outside source, you could just set
> source-address to any.
> 
> 
> On Wed, Feb 4, 2015 at 2:00 PM, Jonathan Call <lordsith49 at hotmail.com>
> wrote:
> I'm in the process of rewriting it all as a static NAT right now.
> 
> Are you applying any IP from routed block to your external interface?
> Reading the rules of proxy-arp suggests that IP range needs to reside on the
> external interface.
> 
> Thanks,
> 
> JonathanDate: Wed, 4 Feb 2015 13:52:00 -0800
> 
> Subject: Re: [j-nsp] NAT on SRX with routed IP range
> 
> From: tyler at adap.tv
> 
> To: lordsith49 at hotmail.com
> 
> CC: juniper-nsp at puck.nether.net
> 
> 
> 
> Ah, sorry, I misunderstood.  We're using static NAT.  Here's a short
> example.
> 
>> show configuration security nat static rule-set static-NATs    from zone
> untrust;rule <name> {    match {        destination-address <external routed
> destination>;        destination-port <external port>;    }    then {
> static-nat {            prefix {                <real host>;
> mapped-port <real port>;            }        }    }}
> 
> 
> 
> 
> 
> 
> 
> On Wed, Feb 4, 2015 at 1:08 PM, Jonathan Call <lordsith49 at hotmail.com>
> wrote:
> 
> 
> 
> 
> 
> 
> 
> I added a proxy-arp enty:
> 
> source {rule-set my-lab-internal {from zone lab-internal;to zone
> untrust;rule my-lab-inet {match {source-address192.168.2.0/26;}then
> {source-nat {interface;}}}}}destination {pool lab-plasma {address
> 192.168.2.2/32 port 8080;}rule-set lab-nats {from zone untrust;rule
> lab-plasma-1 {match {destination-address 4.5.32.16/32;destination-port
> 8080;} then {destination-nat pool lab-plasma;}}}}proxy-arp {interface
> reth0.0 {address {4.5.32.16/32;}}}
> 
> The translation hit counter from 'show security nat destination rule all'
> does not increment so I'm still not hitting the NAT rule. I have the
> appropriate security policy rules between the untrust and lab-internal zones
> to allow 8080 inbound and anything outbound.
> 
> Jonathan
> 
> 
> 
> Date: Wed, 4 Feb 2015 11:45:26 -0800
> 
> Subject: Re: [j-nsp] NAT on SRX with routed IP range
> 
> From: tyler at adap.tv
> 
> To: lordsith49 at hotmail.com
> 
> CC: juniper-nsp at puck.nether.net
> 
> 
> 
> We use routed ranges to NAT a few hosts.  The key for us was configuring
> proxy-arp on the untrust interface for the IPs.
> 
> On Wed, Feb 4, 2015 at 11:24 AM, Jonathan Call <lordsith49 at hotmail.com>
> wrote:
> 
> I've seen plenty of examples of a static NAT where the SRX has a public IP
> range on the untrusted interface. I have not found a good one for when the
> SRX has an IP range routed to it.
> 
> 
> 
> SRX Public IP: 4.5.6.60/30Routed IP range (via the public interface)
> 4.5.32.16/28Trusted zone: 192.168.2.1/26
> 
> 
> 
> show configuration security nat (hopefully this will display properly)
> 
> 
> 
> source {    rule-set my-lab-internal {        from zone lab-internal;
> to zone untrust;        rule my-lab-inet {            match {
> source-address 192.168.2.0/26;            }            then {
> source-nat {                    interface;                }            }
> }    }}destination {    pool lab-plasma {        address 192.168.2.2/32 port
> 8080;    }    rule-set lab-nats {        from zone untrust;        rule
> lab-plasma-1 {            match {                destination-address
> 4.5.32.16/32;                destination-port 8080;            }
> then {                destination-nat pool lab-plasma;            }        }
> }}
> 
> 
> 
> The result of this configuration is that no NAT occurs. But if I change the
> destination-address to the SRX's external IP (4.5.6.60) it works just fine.
> 
> 
> 
> Jonathan
> 
> 
> 
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