Yes: the interfaces are in a security zone and I think there is no a routing configuration error because if I connect a spare device with the IP address of the ISP router, I can ping using my SRX.
We also have another spare device which faces the same issue.
Now we are using the same ISP, the same configuration and same IP addresses and the only difference is the Layer 2 switch that connects our Juniper with their one (in the working case: a Nokia/Siemens).
Non working configuration:
Juniper (on premise) ----- Accedian (layer 2 switch) ----- Juniper (ISP router)
Working (as test) configuration:
Laptop ----- Accedian (layer 2 switch) ----- Juniper (ISP router)
Working (as test) configuration (2)*:
Juniper (on premise) ----- HP Switch ----- Juniper (on premise)
* this configuration only to test if routing/configuration works as expected since is all on-premise
The MAC address retrieved from the laptop is the mac address of the remote router. The ending .105 address is the remote router, while the .107 is the Laptop (in this case) or the 'WAN' interface of the Juniper on-premise.
No. Time Source Destination Protocol Length Info
1 0.000000 Dell_a4:19:d9 Broadcast ARP 42 Who has XXX.XXX.XXX.105? Tell XXX.XXX.XXX.107
Frame 1: 42 bytes on wire (336 bits), 42 bytes captured (336 bits) on interface 0
Ethernet II, Src: Dell_a4:19:d9 (18:03:73:a4:19:d9), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
Address Resolution Protocol (request)
No. Time Source Destination Protocol Length Info
2 0.002308 JuniperN_b7:5f:f0 Dell_a4:19:d9 ARP 56 XXX.XXX.XXX.105 is at 28:c0:da:b7:5f:f0
Frame 2: 56 bytes on wire (448 bits), 56 bytes captured (448 bits) on interface 0
Ethernet II, Src: JuniperN_b7:5f:f0 (28:c0:da:b7:5f:f0), Dst: Dell_a4:19:d9 (18:03:73:a4:19:d9)
Address Resolution Protocol (reply)
No. Time Source Destination Protocol Length Info
3 0.014901 Dell_a4:19:d9 Broadcast ARP 42 Who has XXX.XXX.XXX.105? Tell XXX.XXX.XXX.107
Frame 3: 42 bytes on wire (336 bits), 42 bytes captured (336 bits) on interface 0
Ethernet II, Src: Dell_a4:19:d9 (18:03:73:a4:19:d9), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
Address Resolution Protocol (request)
No. Time Source Destination Protocol Length Info
4 0.017226 JuniperN_b7:5f:f0 Dell_a4:19:d9 ARP 56 XXX.XXX.XXX.105 is at 28:c0:da:b7:5f:f0
Frame 4: 56 bytes on wire (448 bits), 56 bytes captured (448 bits) on interface 0
Ethernet II, Src: JuniperN_b7:5f:f0 (28:c0:da:b7:5f:f0), Dst: Dell_a4:19:d9 (18:03:73:a4:19:d9)
Address Resolution Protocol (reply)
Thanks.