Re: Hardware question

[Jay Acuna via NANOG <nanog () lists nanog org>]

On Mon, Jun 23, 2025 at 10:34 AM Craig Smith via NANOG
<nanog () lists nanog org> wrote:

> Is anyone out there aware of a fail safe switch/router/1U server where upon
> power failure or watchdog event 2 ports would fail to pass through

There are in fact various  "Server bypass NICs".

I would strongly suggest not using it simply to gather telemetry.
Only if the application involves modifying, dropping, or inserting packets
on the link, then you might need that insert of a software-based bridge and
all the drawbacks that come with that.

Bridging is a software function, and using one introduces points of failure,
such as when a server system is powered on, but a software anomaly or the rate
of packets exceeds the CPU's capabilities. You may incur additional latency
in packet forwarding and dropped or corrupted packets. When it comes
to bridges;
many types of network failures are partial failures - a 50% drop rate causes
major troubles, but the OS is still running, and therefore a watchdog
agent sees no issue.

Various units are available which can passively tap a link without inserting
a device that actively participates in the link protocol.   Fiber taps
or copper taps;
depending on the type of link.

Or use the SPAN/Mirror function of existing managed switches which would be less
expensive than implementing a dedicated tap.

Still avoid inserting a software-based
forwarding device between network endpoints  which most likely cannot assure
you full wire speed forwarding with the same consistency as the
hardware ASIC-based
forwarding routers or bridges at either side of the link being tapped,
especially high packet rates on high capacity links.

> Craig
-- 
-JA
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