DHCP bug rOSv6.10 (at least)
Hi Folks, I have received report of this bug behaviour before, but never seen it happen myself, or been able to get any diagnostic at all until this afternoon. Thought I would post in case it is useful info! This has been reported to us previously as "when customer gets DHCP lease, no access to anything is possible. When customer enters static lease, everything is good. Reboot router, everything fine again for a while. Then stops working" Today, I discovered the reason. After some number of leases has been issued by DHCP server, some number in the vicinity of about 200 leases, new leases are issued with bad subnet mask, no gateway and no DNS. End result, of course, is no connectivity. This is apparently just related to number of leases, not actual dhcp server - i.e. the problem happens after the same number of leases are formed even when there are 3 DHCP servers on 4 different subnetworks, or just one DHCP server for all clients. Today, I had a chance to work with a fellow who had done some much better diagnostic work on a network experiencing essentially the same behaviour - he discovered that DHCP becomes broken after some time (or some number of leases) in that clients no longer receive netmask, gateway or DNS detail. Thus the client picks up IP address only, and a default mask (assume based on address 'class') and blank gateway and DNS. The routerOS version in place omn that network is 6.10 - we have upgraded to 6.11 and see if it happens again. If so, we'll grab some pcaps of DHCP traffic and report to MT - in the meantime, if anyone has experience with this issue too, please post it! ;) Cheers, Mike.
Yes, exactly that problem is fixed in that build i linked. It was our mistake, we forget that Option 82 must be at the end of option
Hi Folks, Latest news regarding this issue, MT have confirmed that it is a routerOS bug, and is addressed in v6.12 - Quoting one of the Janises: list,
cause those switches remove all options after option 82. Now it is back in place and there should be no problem and no need to change switch configurations.
Cheers, Mike.
-----Original Message----- From: Public [mailto:public-bounces@talk.mikrotik.com.au] On Behalf Of Mike Everest Sent: Wednesday, 2 April 2014 2:58 PM To: public@talk.mikrotik.com.au Subject: [MT-AU Public] DHCP bug rOSv6.10 (at least)
Hi Folks,
I have received report of this bug behaviour before, but never seen it happen myself, or been able to get any diagnostic at all until this afternoon. Thought I would post in case it is useful info!
This has been reported to us previously as "when customer gets DHCP lease, no access to anything is possible. When customer enters static lease, everything is good. Reboot router, everything fine again for a while. Then stops working"
Today, I discovered the reason. After some number of leases has been issued by DHCP server, some number in the vicinity of about 200 leases, new leases are issued with bad subnet mask, no gateway and no DNS. End result, of course, is no connectivity.
This is apparently just related to number of leases, not actual dhcp server - i.e. the problem happens after the same number of leases are formed even when there are 3 DHCP servers on 4 different subnetworks, or just one DHCP server for all clients.
Today, I had a chance to work with a fellow who had done some much better diagnostic work on a network experiencing essentially the same behaviour - he discovered that DHCP becomes broken after some time (or some number of leases) in that clients no longer receive netmask, gateway or DNS detail. Thus the client picks up IP address only, and a default mask (assume based on address 'class') and blank gateway and DNS.
The routerOS version in place omn that network is 6.10 - we have upgraded to 6.11 and see if it happens again.
If so, we'll grab some pcaps of DHCP traffic and report to MT - in the meantime, if anyone has experience with this issue too, please post it! ;)
Cheers, Mike.
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Mike Everest