I don't have SUP7 to test, but it works on SUP6 and SUP32, I would presume SUP7 retains this functionality.
I've tested between JNPR M320 <-> SUP32, and 'vlan mapping JNPR SUP32' works just fine.
There is no need for QinQ, what the QinQ option does is it adds top tag to one particularly tag. So switchport vlan mapping 1042 dot1q-tunnel 42 would map incoming [1042] stack to [42 1042] stack.
As opposed to switchport vlan mapping 1042 42 which maps incoming dot1q Vlan [1042] to dot1q Vlan [42].
JNPR M320 config:
{master}[edit interfaces ge-0/1/0 unit 1042]
user@m320# show
vlan-id 1042;
family inet {
address 10.42.42.1/24;
}
{master}[edit interfaces ge-0/1/0 unit 1042]
user@m320# run show interfaces ge-0/1/0
Physical interface: ge-0/1/0, Enabled, Physical link is Up
Interface index: 135, SNMP ifIndex: 506
Description: B: SUP32 ge5/1
Link-level type: Flexible-Ethernet, MTU: 9192, Speed: 1000mbps, BPDU Error: None,
MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled, Flow control: Disabled,
Auto-negotiation: Enabled, Remote fault: Online
Device flags : Present Running
Interface flags: SNMP-Traps Internal: 0x4000
CoS queues : 8 supported, 8 maximum usable queues
Current address: 00:12:1e:d5:90:7f, Hardware address: 00:12:1e:d5:90:7f
Last flapped : 2013-02-19 09:14:29 UTC (19w6d 21:12 ago)
Input rate : 4560 bps (5 pps)
Output rate : 6968 bps (4 pps)
Active alarms : None
Active defects : None
Interface transmit statistics: Disabled
SUP32 config:
SUP32#show run int giga5/1
Building configuration...
Current configuration : 365 bytes
!
interface GigabitEthernet5/1
description F: M320 ge-0/1/0
switchport
switchport trunk encapsulation dot1q
switchport mode trunk
switchport nonegotiate
switchport vlan mapping enable
switchport vlan mapping 1042 42
mtu 9216
bandwidth 1000000
speed nonegotiate
no cdp enable
spanning-tree portfast edge trunk
spanning-tree bpdufilter enable
end
SUP32#show ru int vlan42
Building configuration...
Current configuration : 61 bytes
!
interface Vlan42
ip address 10.42.42.2 255.255.255.0
end
SUP32#sh int GigabitEthernet5/1 vlan mapping
State: enabled
Original VLAN Translated VLAN
------------- ---------------
1042 42
SUP32#sh int vlan42
Vlan42 is up, line protocol is up
Hardware is EtherSVI, address is 0005.ddee.6000 (bia 0005.ddee.6000)
Internet address is 10.42.42.2/24
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive not supported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:09, output 00:01:27, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
L2 Switched: ucast: 17 pkt, 1920 bytes - mcast: 0 pkt, 0 bytes
L3 in Switched: ucast: 0 pkt, 0 bytes - mcast: 0 pkt, 0 bytes mcast
L3 out Switched: ucast: 0 pkt, 0 bytes mcast: 0 pkt, 0 bytes
38 packets input, 3432 bytes, 0 no buffer
Received 21 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
26 packets output, 2420 bytes, 0 underruns
0 output errors, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
And
SUP32#ping 10.42.42.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.42.42.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms
SUP32#sh arp | i 10.42.42.1
Internet 10.42.42.1 12 0012.1ed5.907f ARPA Vlan42
SUP32#show mac address-table dynamic address 0012.1ed5.907f
Legend: * - primary entry
age - seconds since last seen
n/a - not available
vlan mac address type learn age ports
------+----------------+--------+-----+----------+--------------------------
Active Supervisor:
* 450 0012.1ed5.907f dynamic Yes 0 Gi5/1
* 50 0012.1ed5.907f dynamic Yes 0 Gi5/1
* 40 0012.1ed5.907f dynamic Yes 0 Gi5/1
* 42 0012.1ed5.907f dynamic Yes 5 Gi5/1
user@m320# run ping 10.42.42.2 count 2
PING 10.42.42.2 (10.42.42.2): 56 data bytes
64 bytes from 10.42.42.2: icmp_seq=0 ttl=255 time=0.495 ms
64 bytes from 10.42.42.2: icmp_seq=1 ttl=255 time=0.651 ms
--- 10.42.42.2 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max/stddev = 0.495/0.573/0.651/0.078 ms
{master}[edit interfaces ge-0/1/0 unit 1042]
user@m320# run show arp no-resolve |match 10.42.42.2
00:05:dd:ee:60:00 10.42.42.2 ge-0/1/0.1042 none
Not all together happy with how this post turned out, but I've learned things that I didn't know before, so that's good.
For example, normally if two nodes (A and B) are connected to a switch which is on the downstream side of another device like your firewall, the switch will route packets from A -> B and vise versa without contacting anything upstream (from @Tedwin).
I decided to post my own answer with the good parts from the comments with @Panther Modern.
Use higher quality hardware. Since I'm using Netgear ProSafe unmanaged switches, I'm considering upgrading to something like Cisco. @Mike Pennington suggested the SG300 series, which I have researched before and found on Amazon for less than $200. @Panther Modern suggests Arista, Cisco, Juniper and Brocade switches.
Troubleshoot each piece independently and isolate the problem. I've done some of this, to the extent that I have isolated the general path, but in an environment where 100% uptime makes people happy and allows them to get work done, this can be tricky. But point taken...
Consider topology and where you have access to and how many users you have. These factors can influence your choices for gear and how you go about answering your questions.
Find good networking tools and use those to help troubleshoot your issue. pfSense helped a lot concerning traffic that passed through the firewall. I also learned about Robocopy for limiting traffic on the client. This tool works pretty well.
Best Answer
This is only something you can decide for yourself. Answers are likely to be opinion-based, so this question may be closed as off-topic for this forum. I will try to give you the facts without the opinion.
The main reasons you would get SmartNet are for service, support, and software updates. If there are bugs in your code version that get updated in later releases, or new features are added to new releases, SmarNet allows you to easily download the new code from CCO. You can also call CCO for help with the devices covered by the contract. Cisco will also cover failed devices and replace them for you.
The only real reason you wouldn't get it is cost. There are several levels of support, from Next Business Day to 2-hour turnaround, and pricing is based on the support level.