Mysterious in by router

[PavelBab]

Hi,
I use router RT-N16 router with Netgear DM200 modem (in bridge mode).
With official firmware and also with Merlin firmware some of HTTP web services times-out or throws "Connection has been reset" message while transferring data (for example submitting POST data through web form).
With old firmwares made by Oleg or Igor I have no problem.
Does anybody have any idea how to make new firmware work.

Thanks

 

[pete y testing]

Does anybody have any idea how to make new firmware work.

the n16 is no longer supported by ether asus or merlin

prob time to get a new router

 

[PavelBab]

the n16 is no longer supported by ether asus or merlin

prob time to get a new router

I tested the latest fork of Merlin FW. Due to same family of FW the new router will have same problem.

 

[RMerlin]

Turn off your modem for 10-20 minutes.

 

[joegreat]

the n16 is no longer supported by ether asus or merlin

...but still by John's fork of 374.43!

 

[PavelBab]

...but still by John's fork of 374.43!

Thank you for your help.
RMerlin: Turn off the modem do not solve this problem.
Joegreat: I am testing the John's fork. A long time I used the Oleg FW, next Igor ones. I decided to use new generation of FW in this time.

 

[PavelBab]

Hi Gui,
I founded the problem. There is an error in the new firmware generation (version 3.0.xx).
I tested following routers:
- RT-N16 with old firmware generation (version 1.9.2.7.xxx)
- Zyxel VMG1312
- Netgear DM200 (in router mode)
All above mentioned routers work with MTU equal 1492 (according to specification of my provider).
Router RT-N16 with new generation of firmware does not work with MTU values higher than 1484. (Tested stock, Merlin, John's, ... firmwares)

Why it is necessary to set MTU value in new firmware generation lower than recommended.

 

[joegreat]

All above mentioned routers work with MTU equal 1492 (according to specification of my provider).
Router RT-N16 with new generation of firmware does not work with MTU values higher than 1484. (Tested stock, Merlin, John's, ... firmwares)
Why it is necessary to set MTU value in new firmware generation lower than recommended.

Really?

On my AC87U all MTU values are set to 1500 (expect loop back) - and same on the N66U:
chief@RT-AC87U:/tmp/home/root# ip ad | grep mtu
1: lo: <LOOPBACK,MULTICAST,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
2: ifb0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN qlen 32
3: ifb1: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN qlen 32
4: aux0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
5: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
6: eth1: <BROADCAST,MULTICAST,ALLMULTI,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 16
7: vlan1@eth0: <BROADCAST,MULTICAST,ALLMULTI,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP
8: vlan2@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP
9: br0: <BROADCAST,MULTICAST,ALLMULTI,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
10: wl0.3: <BROADCAST,MULTICAST,ALLMULTI,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 16
11: tun11: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 100

You can test the best MTU for your provider with this homepage - to not forget to allow WAN ping responses in the firewall settings (otherwise the test will not work).

 

[PavelBab]

Realy,
I set MTU 1500 and I tested it by ping command:
ping 8.8.8.8 -f -s 1456 -i 200
It is mean that MTU=1456+28=1484
Higher value cause loss of packet. More over HTTP services are OK for MTU 1484.

PS: thank you. I am testing it.

 

[mstombs]

Can't use more than 1492 with PPPoE connections since 8 bytes overhead needs to be added. What sort of bridge mode is the DM200 in ? You cannot full-bridge PPPoA connections, some modems pretend to use some form of half-bridge, I see this is still causing confusion with this modem :- https://community.netgear.com/t5/DS...s-using-DM200-in-modem-only-mode/td-p/1132247

 

[PavelBab]

OK. Maybe you are right.
I have no any detail information about the Modem mode. I use PPPoE setup in the router.
Lower MTU is not big issue. I know when my router die I can buy new Asus again. I know how to solve it now.

Thanks to all.