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teleport
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RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Fri Jun 24, 2022 2:42 am

have an Rb260GS switch which had been working great for about 1.5 years. recently the computers connected to the switch were finding it difficult to get DHCP IP address. the switch is in turn connected to an RB450GX4 up stream router(also DHCP server).
to isolate the issue to the switch, replaced the RB260GS to an old switch and connected devices work great.
noticed that rb260GS tries to keep renewing every 15seconds from the upstream RB450GX4 router.also logging into web ui console was slow and fleeting(as it keeps renewing)
does any one have any idea why this is happening suddenly?
 
mkx
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Fri Jun 24, 2022 12:18 pm

Could be the switch is loosing upstream connectivity (port flapping). Which then triggers DHCP lease re-acquisition. Does RB450Gx4 log show anything suspicious about ethernet port, connected to RB260GS?
 
teleport
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Fri Jun 24, 2022 6:24 pm

attached is the debug log from the upstream dhcp server.(rb450gx4)..notice every 15 seconds..there is activity..
You do not have the required permissions to view the files attached to this post.
 
mkx
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Fri Jun 24, 2022 8:31 pm

And nothing else about that device or ethernet port through which it connects?

Did you try to reboot RB260GS?
 
teleport
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Fri Jun 24, 2022 8:41 pm

And nothing else about that device or ethernet port through which it connects?

Did you try to reboot RB260GS?
Reboot did not help. Any specific logging levels on rb450gx4? Just had dhcp logging level on apart from standard log levels .
 
mkx
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Sat Jun 25, 2022 5:59 pm

Port flapping (intermittent connection losses) should be shown in logs even with default logging settings. And those would explain frequent DHCP lease renewals.

What about lease time setting on your DHCP server? It seems that too short setting (e.h. shorter than a few tens of minutes) can upset some clients. Not sure about SwOS device as DHCP client.
 
teleport
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Sat Jun 25, 2022 7:19 pm

Port flapping (intermittent connection losses) should be shown in logs even with default logging settings. And those would explain frequent DHCP lease renewals.

What about lease time setting on your DHCP server? It seems that too short setting (e.h. shorter than a few tens of minutes) can upset some clients. Not sure about SwOS device as DHCP client.
played around with that too..12 hrs was initial.then changed to 8 hours.both cases at end of 15 seconds it asks for lease again in a perpetual loop..changed power supply from PoE to dedicated power..same issue..introduced third party switch in between. still same behavior.
 
teleport
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Sat Jun 25, 2022 8:22 pm

Port flapping (intermittent connection losses) should be shown in logs even with default logging settings. And those would explain frequent DHCP lease renewals.

What about lease time setting on your DHCP server? It seems that too short setting (e.h. shorter than a few tens of minutes) can upset some clients. Not sure about SwOS device as DHCP client.
played around with that too..12 hrs was initial.then changed to 8 hours.both cases at end of 15 seconds it asks for lease again in a perpetual loop..changed power supply from PoE to dedicated power..same issue..introduced third party switch in between. still same behavior.
Here is latest findings:
removed RB450GX4 and placed thirparty router in between. RB260GS works great and no issues with DHCP.
Removed RB260GS and placed thirdparty switch in between. this also works fine.

clearly, the issue seems to be RB260GS facing issues with DHCP on recent versions of RouterOS firmware. i started seeing this on 7.3 and later.
 
teleport
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Sat Jun 25, 2022 8:40 pm



played around with that too..12 hrs was initial.then changed to 8 hours.both cases at end of 15 seconds it asks for lease again in a perpetual loop..changed power supply from PoE to dedicated power..same issue..introduced third party switch in between. still same behavior.
Here is latest findings:
removed RB450GX4 and placed thirparty router in between. RB260GS works great and no issues with DHCP.
Removed RB260GS and placed thirdparty switch in between. this also works fine.

clearly, the issue seems to be RB260GS facing issues with DHCP on recent versions of RouterOS firmware. i started seeing this on 7.3 and later.
downgrade to 7.2.3 fixed the issue. seems to be regression crept into newer releases. can someone bring this to attention of mikrotik developers. thanks
 
mkx
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Sat Jun 25, 2022 11:16 pm



Here is latest findings:
removed RB450GX4 and placed thirparty router in between. RB260GS works great and no issues with DHCP.
Removed RB260GS and placed thirdparty switch in between. this also works fine.

clearly, the issue seems to be RB260GS facing issues with DHCP on recent versions of RouterOS firmware. i started seeing this on 7.3 and later.
downgrade to 7.2.3 fixed the issue. seems to be regression crept into newer releases. can someone bring this to attention of mikrotik developers. thanks

Nice catch. There are already reports about various DHCP clients having issues with DHCP server in 7.3 (and AFAIK 7.4beta). Seems that option order in DHCP lease offers is different than it used to be (and different from what most other servers do) and this seems to upset some clients ... and from your findings it seems that MT's own DHCP client in SwOS gets upset as well.

You may want to report the problem (referring to this topic) to MT support, e.g. via e-mail sent to support@mikrotik.com
 
teleport
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Sun Jun 26, 2022 1:43 am



downgrade to 7.2.3 fixed the issue. seems to be regression crept into newer releases. can someone bring this to attention of mikrotik developers. thanks

Nice catch. There are already reports about various DHCP clients having issues with DHCP server in 7.3 (and AFAIK 7.4beta). Seems that option order in DHCP lease offers is different than it used to be (and different from what most other servers do) and this seems to upset some clients ... and from your findings it seems that MT's own DHCP client in SwOS gets upset as well.

You may want to report the problem (referring to this topic) to MT support, e.g. via e-mail sent to support@mikrotik.com
Done. thanks.
 
teleport
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Tue Jun 28, 2022 4:02 pm

From Support:
"We have managed to reproduce the issue locally in our labs and look forward to fixing it on upcoming Router OS versions, unfortunately, I cannot provide an ETA now."

if anyone wants this issue to be prioritized so that they can use container feature or anything else new in 7.3 and above, please make your voice known by raising additional support case.i have not been able to reason with support with my comments that their own switch(and everything connected to it) becomes unusable on latest/flagship 7.x release and essentially stopped upgrade path beyond 7.2.3.
 
mkx
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Wed Jun 29, 2022 10:43 pm

From ROS 7.4beta5 change log:
*) dhcpv4-server - placed option 53 as the first one in the packet;
So maybe you can upgrade your RB450Gx4 to latest beta and see if things got any better?
 
teleport
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Thu Jun 30, 2022 3:21 am

From ROS 7.4beta5 change log:
*) dhcpv4-server - placed option 53 as the first one in the packet;
So maybe you can upgrade your RB450Gx4 to latest beta and see if things got any better?
did that too on 74beta5. issue still persists.support has been given supout.rif even on latest beta (beta5)
 
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Tue Jul 12, 2022 11:21 pm

From ROS 7.4beta5 change log:



So maybe you can upgrade your RB450Gx4 to latest beta and see if things got any better?
did that too on 74beta5. issue still persists.support has been given supout.rif even on latest beta (beta5)
can someone acknowledge that they have also run into same issue(even in latest bets5/rc2). am having hard time convincing support something that is easily reproducible.
 
teleport
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Fri Jul 15, 2022 4:28 am



did that too on 74beta5. issue still persists.support has been given supout.rif even on latest beta (beta5)
can someone acknowledge that they have also run into same issue(even in latest bets5/rc2). am having hard time convincing support something that is easily reproducible.
works fine with default router settings of router . this issue shows up for specific scenario of VLAN configuration.
if you have RB260 connected to the router port and the router port is assigned a default VLANID and if it is different than the previous router port's default VLAN Id (/switch/port), then it triggers the issue.
if the default vlan ids are same, then it works.
 
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Fri Jul 15, 2022 5:41 am

have you discarded STP/RSTP issues? which version of SwOS are you using?

is OLD RB260GS which supports only up to SwOS 1.7 or the later version RB260GS(CSS106-5G-1S) which supports up to SwOS 2.13 ?
 
teleport
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Fri Jul 15, 2022 6:47 am

have you discarded STP/RSTP issues? which version of SwOS are you using?

is OLD RB260GS which supports only up to SwOS 1.7 or the later version RB260GS(CSS106-5G-1S) which supports up to SwOS 2.13 ?
recent one RB260GS(CSS106-5G-1S) which supports up to SwOS 2.13
 
teleport
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable  [SOLVED]

Tue Jul 19, 2022 10:25 pm

have you discarded STP/RSTP issues? which version of SwOS are you using?

is OLD RB260GS which supports only up to SwOS 1.7 or the later version RB260GS(CSS106-5G-1S) which supports up to SwOS 2.13 ?
recent one RB260GS(CSS106-5G-1S) which supports up to SwOS 2.13
Issue Resolved:

From Support:
It is related to RSTP. The RB450Gx4 with HW offloaded bridge and configured VLANs on the switch menus tags RSTP BPDUs from CSS106. These tagged BPDUs are received on the CPU and they should be ignored based on the IEEE standard. Since RouterOS 7.3 we have made a software fix that ignores such packets. So after upgrade to 7.3, these two devices always tries and fails to negotiate the root bridge and cause DHCP related problems.

The related changelog entry:
*) bridge - ignore VLAN tagged BPDU;

The problem is that switch chip on RB450Gx4 does not correctly treat the BPDUs. We will try to improve this in future releases, but I cannot provide a release date.

Some possible workarounds:
1. Disable RSTP on RB450Gx4 (/interface bridge set protocol-mode=none) or CSS106.
2. Configure a switch rule to redirect the BPDUs to the CPU, for example:
/interface ethernet switch rule
add dst-mac-address=01:80:C2:00:00:00/FF:FF:FF:FF:FF:FF ports=AP1,RBSSwitchConnectedPort,UnifiAP redirect-to-cpu=yes switch=RBGX4Switch
 
teleport
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Re: RB260GS issue(DHCP keeps renewing every 15 seconds) and devices connected are not stable

Fri Jul 29, 2022 9:28 pm



recent one RB260GS(CSS106-5G-1S) which supports up to SwOS 2.13
Issue Resolved:

From Support:
It is related to RSTP. The RB450Gx4 with HW offloaded bridge and configured VLANs on the switch menus tags RSTP BPDUs from CSS106. These tagged BPDUs are received on the CPU and they should be ignored based on the IEEE standard. Since RouterOS 7.3 we have made a software fix that ignores such packets. So after upgrade to 7.3, these two devices always tries and fails to negotiate the root bridge and cause DHCP related problems.

The related changelog entry:
*) bridge - ignore VLAN tagged BPDU;

The problem is that switch chip on RB450Gx4 does not correctly treat the BPDUs. We will try to improve this in future releases, but I cannot provide a release date.

Some possible workarounds:
1. Disable RSTP on RB450Gx4 (/interface bridge set protocol-mode=none) or CSS106.
2. Configure a switch rule to redirect the BPDUs to the CPU, for example:
/interface ethernet switch rule
add dst-mac-address=01:80:C2:00:00:00/FF:FF:FF:FF:FF:FF ports=AP1,RBSSwitchConnectedPort,UnifiAP redirect-to-cpu=yes switch=RBGX4Switch
changing bridge priority on the router (from 8000 to 7000) solves (root bridge) the issue too (and it makes bridge ports designated ports)

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