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New Member

L3 Span

Simple question. Is it possible to SPAN over L3.

bjw Silver

Re: L3 Span

SPAN related to an interface of port, and all the traffic that passes it.

The Switched Port Analyzer (SPAN) enables you to mirror traffic on any port for analysis by a sniffer or RMON probe. The SPAN directs traffic from a GigEthernet Ethernet or Fast Ethernet port or VLAN to an GigEthernet Ethernet or Fast Ethernet monitor port for detailed analysis and troubleshooting.

You can monitor a single port or VLAN using a sniffer or remote monitoring (RMON) probe like the a Cisco SwitchProbe.

An RMON probe analysis of the remaining five RMON groups.

The closest you might get to specific L3 information would be to span a VLAN that might pass traffic over the L3 subnet that you are looking for.

New Member

Re: L3 Span

This deosn't really answer the question I am asking.

I want to monitor a port or VLAN on a switch and set the destination port as a port on another switch that is not part of the same L2 network (so I can't use RSPAN).

bjw Silver

Re: L3 Span

I think you can use RSPAN, it uses an RSPAN VLAN that brings a source port on a switch to a destination port on a 2nd switch and the source vlan is configurable in RSPAN.

Theoretically it trunks the SPAN session to wherever you need it using a dedicated RSPAN VLAN. But note that RSPAN doesn't support L2 stuff like CDP, DTP, etc. I always recommend spanning locally when possible.

Check out the RSPAN configs: