WRT1900ac DSA Subsystem Configuration Question

Installing and Using OpenWrt
1

I have been looking at some old forum posts related to the DSA switch architecture switch over and devices with multiple cpu ports like my wrt1900ac(v1).

Back then it seemed like the consensus was that DSA only supported one cpu port and ever since then the network config has (on my wrt1900ac) reflacted this. I see that eth1 is still detected and everything but not utilized.

My questions are:

  1. Does the single cpu port restriction still apply for DSA?
  2. Can eth1 be configured at all on my device?
  3. Isn't using just the single cpu port --eth0 on the wrt1900ac-- bottle necking the throughput basically in half considering the way it is designed? I am planning on testing it this weekend to see if that is in fact the case.

I could not find any recent discussion on if it was ever fixed.

2

O. your router is not ipq80xy

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3

I think the last update is in https://github.com/openwrt/openwrt/pull/4982 fyi @anomeome
So its not supported out of the box

4

Ya, I know but they were discussing the general topic in regards to DSA and multi cpu ports. Unless I accidentally copied the wrong link, it also had multiple cpu ports on that hardware I believe; however, the hardware and setup was different. I just added it for informational purposes.

5

Thanks. That is closer to what I was looking for; however, it is mentioned that the core issue in regards to netdev is assigning a LAG as the cpu master (the LAG containing both cpu ports). It seems like the workarounds mentioned are related to ipq806x again.

Isn't the eth1 port on the WRT series routers not really a switch port and basically just bound to the WAN physical port anyways? Guess I can test it out tonight.

6

just like mediateks - one port directly to the phy another to the dsa.

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7
  • AFAIK issue is still extent
  • there were a few attempts at resolution (as per above), but upstream had apparently taken another tack so all were rejected here, but I have never seen anything come down the pipe
  • to be of noticeable impact you would need to be on a symmetrical ~1G pipe or better.
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8

It uses both mii-s on SoC, just that one is hardwired to WAN, ie not 100% flexible as in swconfig.

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9 
root@bsaedgy:~# ls -l /sys/class/net
lrwxrwxrwx    1 root     root             0 Dec 31  1969 eth0 -> ../../devices/platform/soc/soc:internal-regs/f1070000.ethernet/net/eth0
lrwxrwxrwx    1 root     root             0 Oct  9 13:56 ifb-wan -> ../../devices/virtual/net/ifb-wan
lrwxrwxrwx    1 root     root             0 Dec 31  1969 lan1 -> ../../devices/platform/soc/soc:internal-regs/f1072004.mdio/mdio_bus/f1072004.mdio-mii/f1072004.mdio-mii:00/net/lan1
lrwxrwxrwx    1 root     root             0 Dec 31  1969 lan2 -> ../../devices/platform/soc/soc:internal-regs/f1072004.mdio/mdio_bus/f1072004.mdio-mii/f1072004.mdio-mii:00/net/lan2
lrwxrwxrwx    1 root     root             0 Dec 31  1969 lan3 -> ../../devices/platform/soc/soc:internal-regs/f1072004.mdio/mdio_bus/f1072004.mdio-mii/f1072004.mdio-mii:00/net/lan3
lrwxrwxrwx    1 root     root             0 Dec 31  1969 lan4 -> ../../devices/platform/soc/soc:internal-regs/f1072004.mdio/mdio_bus/f1072004.mdio-mii/f1072004.mdio-mii:00/net/lan4
lrwxrwxrwx    1 root     root             0 Dec 31  1969 lo -> ../../devices/virtual/net/lo
lrwxrwxrwx    1 root     root             0 Oct  9 08:37 switch0 -> ../../devices/virtual/net/switch0
lrwxrwxrwx    1 root     root             0 Oct  9 08:37 switch0.10 -> ../../devices/virtual/net/switch0.10
lrwxrwxrwx    1 root     root             0 Oct  9 08:37 switch0.20 -> ../../devices/virtual/net/switch0.20
lrwxrwxrwx    1 root     root             0 Oct  9 08:37 switch0.40 -> ../../devices/virtual/net/switch0.40
lrwxrwxrwx    1 root     root             0 Oct  9 08:37 teql0 -> ../../devices/virtual/net/teql0
lrwxrwxrwx    1 root     root             0 Dec 31  1969 wan -> ../../devices/platform/soc/soc:internal-regs/f1072004.mdio/mdio_bus/f1072004.mdio-mii/f1072004.mdio-mii:00/net/wan
root@bsaedgy:~# brctl show
bridge name	bridge id		STP enabled	interfaces
switch0		7000.6038e0b89eb1	yes		lan4
							lan2
							lan3
							lan1
1 Like
10

Maybe snapshot is needed, at least upstream for that platform has split configā€¦.

11

Off of a rango but mamba be the same

 OpenWrt SNAPSHOT, r31387-1949fb996a
 -----------------------------------------------------
root@bsaedgy:~# uname -a
Linux bsaedgy 6.12.51 #0 SMP Thu Oct  9 14:37:25 2025 armv7l GNU/Linux
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12

Thats rsther bad then, i dunno why upstream dts id not used.

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13

@anomeome Thank you for the information. I am getting FTTH soon with 1gbit at an affordable price so that is why I am inquiring. It is residential service though and I do not know much about the company; it may be some way over provisioned GPON that I will never see those speeds consistently anyways. I noticed eth1 is listed still when I run ip link list so I wasn't sure.

Ok. Thanks for the info. I plan on testing this tonight to find out for myself but since I am here: do you know if I were to then assign the wan interface to eth1 --no vlans or anyting-- if it would work (basically how it used to be with swconfig, but specifically just the wan/eth1 part of the config? Also, I am using the latest stable release. Maybe I will try flashing snapshot to the other partition if I have issues.