Re: [nsp] 10Mb eth question

From: Rick Burts (
Date: Fri Jan 25 2002 - 10:52:31 EST


If the 2500 is not a trunk the switch will see it as a member of a
single VLAN and will only forward traffic to it from stations in the
same VLAN. The router will forward back out the same interface if it
determines that it needs to forward a packet and the destination is out
that interface. If one station on a switch port needs to send to
station on another port of the switch (in the same VLAN) they would
normally talk directly to each other. If the two stations (in the
same VLAN) were defined as belonging to two different subnets and if
the stations defined your 2500 as their default gateway then one station
would send to the 2500 which would forward to the destination back out
the same Ethernet interface. Yes you can do it but I doubt that this is
really what you had in mind.

You could do interVLAN routing on the 2500 if the router had two
interfaces. Connect one Ethernet to one switch port (member of one VLAN
and in one subnet) and connect the second Ethernet to another switch
port (member of a different VLAN and in a different subnet). Now you
have interVLAN routing on a 2500 router.


Birsen Ozturk wrote:
> Hello all
> I have a Cisco2500 ethernet connected to a switch. The 2500 is supposed to
> route back the traffic comming from Eth0 back to Eth0 if the destination of
> the traffic is another router connected to another port of the same switch.
> Will my 2500 do that(the Eth0 is 10Mb and half-duplex so I cannot make it
> trunk). i.e. can I make something similar to "router-on-a-stick" topology
> without VLANs on 10Mb half-duplex port?
> Thanks in advanace
> Birsen

Rick Burts     CCIE 4615  CCSI     Email: 
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