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TedRule
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Joined: Tue Nov 03, 2020 4:41 pm

Lack of support for CDPv2

Fri Jul 16, 2021 11:09 am

We have recently noticed that some of our VMWare ESXi machines are seemingly not visible via CDP in the local MikroTik Switch's Neighbour Discovery, despite CDP being enabled on VMWare,
and CDP being enabled in RouterOS Discovery.

The problem appears to be that RouterOS fails to decode CDPv2 packets, but is perfectly happy to decode CDPv1.

Meanwhile, it seems that modern Cisco Switches themselves dual-advertise with both CDPv1 and CDPv2 packets, MikroTik Switches advertise with only CDPv1, but VMWare apparently
only advertises with CDPv2.

From what I can see from a Wireshark capture of the innards of a pair of CDPv1 and CDPv2 packets from a Cisco Switch, it seems that the format is eminently backwards-compatible;
CDPv2 just advertises more features in additional TLV sub-sections after the sections which are contained in a CDPv1 packet, and they both use the same MAC Multicast Address.

I haven't yet been able to prove whether CDPv1 advertisements are correctly parsed by VMWare, but I hope to rejig some of our kit shortly to prove whether this is the case.

All in all, could you add CDPv2 receive parsing to RouterOS, please, so that we can see our VMWare machines' advertisements, please?
 
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jimmer
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Joined: Wed Mar 06, 2019 10:06 am
Location: Tasmania, Australia

Re: Lack of support for CDPv2

Fri Jul 16, 2021 11:11 am

+1 for CDPv2 packet support as well.

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