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Today's Topics:
1. Port VLAN mismatches (Clayton Tavernier)
2. Re: Port VLAN mismatches (Clayton Tavernier)
3. Re: Port VLAN mismatches ([email protected])
--- Begin Message ---
I'm new to Netdisco and while poking around Reports I found I have 18 Port
VLAN Mismatches and I'm not sure what to do with this information.
All my left devices are managed switches with no vlans set up (so all
"n:1"). My right devices have vlans defined.
I assume the problems are on the right sides but I don't know what the
problems are or what to do about them.
Suggestions?
Thanks.
--- End Message ---
--- Begin Message ---
Thanks, I was mostly trying to figure out what the report was telling me
but I appreciate the tutorial. My vlan-fu isn't great.
On Wed, Aug 8, 2018 at 11:47 AM, [email protected] <[email protected]>
wrote:
> I think your question is more a network management question than Netdisco,
> but I'll give it a try.
>
>
>
> As a general principle, you want the VLAN settings on connections between
> switches to match. There are exceptions.
>
>
>
> The first thing that usually needs to match is trunking: you want them
> trunked or access mode on both side, and if trunked the same protocol.
> Some switches have a "general" or similar mode that figures it out, but at
> the core to be effective trunking mode needs to match.
>
>
>
> If trunked, you generally would expect the allowed list (and native if
> declared) to match as well. if you have an allowed list on one side that
> is 2,3,4,5 and on the other side 3,4,5,6, then vlan's 2 and 6 will not
> communicate across that trunk. You may or may not get any error (mostly
> not).
>
>
> If access mode, and you have something like VLAN 3 access on one side and
> VLAN 5 on the other side, then VLAN 3 will leak into 5, and vice versa --
> it will implicitly convert VLAN ID's across the link because the link is
> access mode and nothing is tagged. The same sort of thing can happen if
> the native vlan is different on each end.
>
>
>
> Some people use those weird scenarios, for example if you need to
> translate VLAN ID's and do not have a switch capable of it, the mis-matched
> access mode will work.
>
>
>
> I hasten to add that there's a lot more to making sure things are
> compatible, from spanning tree compatibility to any vlan definition
> protocols (e.g. cisco vtp). But as a starting point, trunks between
> switches that do not have a matching allowed (and native) list on each side
> at minimum deserve a careful look, which is the purpose of the VLAN
> mismatch report.
>
>
>
> Linwood
>
>
>
>
>
> *From:* Clayton Tavernier [mailto:[email protected]]
> *Sent:* Wednesday, August 8, 2018 2:09 PM
> *To:* [email protected]
> *Subject:* [Netdisco] Port VLAN mismatches
>
>
>
> I'm new to Netdisco and while poking around Reports I found I have 18 Port
> VLAN Mismatches and I'm not sure what to do with this information.
>
>
>
> All my left devices are managed switches with no vlans set up (so all
> "n:1"). My right devices have vlans defined.
>
>
>
> I assume the problems are on the right sides but I don't know what the
> problems are or what to do about them.
>
>
>
> Suggestions?
>
>
>
> Thanks.
>
>
>
>
>
--
Clayton Tavernier
Network Computer Technician
Pleasanton Unified School District
925-426-4292
PUSD Tech Support Center
https://rt.pleasanton.k12.ca.us/
--- End Message ---
--- Begin Message ---
I think your question is more a network management question than Netdisco, but
I'll give it a try.
As a general principle, you want the VLAN settings on connections between
switches to match. There are exceptions.
The first thing that usually needs to match is trunking: you want them trunked
or access mode on both side, and if trunked the same protocol. Some switches
have a "general" or similar mode that figures it out, but at the core to be
effective trunking mode needs to match.
If trunked, you generally would expect the allowed list (and native if
declared) to match as well. if you have an allowed list on one side that is
2,3,4,5 and on the other side 3,4,5,6, then vlan's 2 and 6 will not communicate
across that trunk. You may or may not get any error (mostly not).
If access mode, and you have something like VLAN 3 access on one side and VLAN
5 on the other side, then VLAN 3 will leak into 5, and vice versa -- it will
implicitly convert VLAN ID's across the link because the link is access mode
and nothing is tagged. The same sort of thing can happen if the native vlan
is different on each end.
Some people use those weird scenarios, for example if you need to translate
VLAN ID's and do not have a switch capable of it, the mis-matched access mode
will work.
I hasten to add that there's a lot more to making sure things are compatible,
from spanning tree compatibility to any vlan definition protocols (e.g. cisco
vtp). But as a starting point, trunks between switches that do not have a
matching allowed (and native) list on each side at minimum deserve a careful
look, which is the purpose of the VLAN mismatch report.
Linwood
From: Clayton Tavernier [mailto:[email protected]]
Sent: Wednesday, August 8, 2018 2:09 PM
To: [email protected]
Subject: [Netdisco] Port VLAN mismatches
I'm new to Netdisco and while poking around Reports I found I have 18 Port VLAN
Mismatches and I'm not sure what to do with this information.
All my left devices are managed switches with no vlans set up (so all "n:1").
My right devices have vlans defined.
I assume the problems are on the right sides but I don't know what the problems
are or what to do about them.
Suggestions?
Thanks.
--- End Message ---
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