Hello friends. I came across a strange problem. After adding a few switches to the l2 backbone, I found that the romon frames do not pass through them. The switchеs are Cisco WS-C2960L-SM-24TS and romon discovery protocol does not detect other devices after them . Everything else works perfectly like port Trunk and Access. Does anyone have a solution to this problem ?
Can anyone help, i haven’t solved the problem yet?
Do the Cisco switches block the RoMON multicast address [01:80:c2:00:88:bf] or ethertype 0x88bf due to either a bug or IGMP filtering?
Some other switches seem to have issues, e.g. https://community.cisco.com/t5/small-business-switches/how-to-report-a-bug-without-a-contract-sg200-switch/td-p/4307249
Certainly the non-standard ethertype 0x88bf could be dropped by some defaults on a cisco etc., something to look for.
You may also want make sure the Mikrotik is sending RoMON out too… Depending on how your dealing with VLAN (e.g. via switch chip or vlan-filtering or “dumb switch”), it’s possible it might not even be leaving the Mikrotik.
I say this since there are a lot of “notes” in the various Bridging/Switch help.mikrotik.com docs, like this one, with potential “gotchas”:
Bridge HW vlan-filtering was added in the RouterOS 7.1rc1 (for RTL8367) and 7.1rc5 (for MT7621) versions. The switch does not support other ether-type 0x88a8 or 0x9100 (only 0x8100 is supported) and no tag-stacking. Using these features will disable HW offload.
See also http://forum.mikrotik.com/t/is-romon-broken-in-7-1-1/154704/1 . Again, not sure that your issue, more highlighting that the 0x88bf ethertype is what you need to see/allow on the L2 switching plane (& ethertype 0x8100 = “normal” VLANs) .
Thanks for the answers!
My network backbone is made of old models cisco switchs - types of 2950 and 2960. Nothing special - access ports and trunks! My main router is mikrotik and i use few of cAPs ~ 20 units.Оn the mikrotik devices I do not use vlans. When i replace the 2950 with new one switch and the problem appears!