From: Mohammad Saeed (mzsaeed@gmail.com)
Date: Sun Feb 04 2007 - 03:02:10 ART
Excellent....The question was raised when one of my colleague, he told
me that he has split the GigabitEthernet interface on the router in to
multiple interface, like g0/0.1, g0/0.2, g0/0.3 and those interfaces
are on different networks. This G0/0 is physically connected to a port
on 2950, which is in trunk mode with DOT1Q encapsulation. He said that
he is running EIGRP to route between these networks which he has
assigned to subinterfaces of G0/0. I told him that you don't need to
run rotuing protocol to route between directly connected networks as
router already has these networks in its RT. AM I RIGHT???
But here in my lab I tried the same on Frame-Relay, and you all are
excellent in your profession...:):):) so, here it is basically Layer 2
issue.....
Thank you very much every body who replied.......
With best regards,
Mohammad Zahed Saeed
On 2/3/07, Brian Dennis <bdennis@internetworkexpert.com> wrote:
> <quote>
> Because as I understand, R1 will send the packets for any destination to R5
> </quote>
>
> The problem is that you are not sending packets for any destination to R5.
> You are sending packets for any destination out Serial0/0. If Serial0/0 is a
> point-to-point interface then it will be sent to the remote end-point. This
> is because there can only be one 3 to layer 2 mapping on a P2P interface and
> because of this all packets use that layer 3 to layer 2 mapping.
>
> If Serial0/0 is a multipoint interface (i.e. physical Frame Relay interface
> or multipoint subinterface) then there can be more than one remote end-point
> and hence more than one layer 3 to layer 2 mapping. In this case the router
> does not have a layer 3 to layer 2 mapping for the destination (173.23.23.5)
> and in turn drops the packet. To resolve this you can either configure the
> static route to point to R5's IP address across the Serial0/0 interface
> (preferred solution) or create a layer 3 to layer 2 mapping for 173.23.23.5
> on the DLCI to R5.
>
> The general rule is that when using static routes in a WAN environment you
> shouldn't point the static route to an interface if it is a multipoint
> interface.
>
> --
>
> Brian Dennis, CCIE4 #2210 (R&S/ISP-Dial/Security/SP)
> bdennis@internetworkexpert.com
>
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
> Toll Free: 877-224-8987
> Direct: 775-745-6404 (Outside the US and Canada)
>
>
> On 2/3/07 8:55 PM, "Mohammad Saeed" <mzsaeed@gmail.com> wrote:
>
> > Hi,
> >
> > Sorry, my last email I didn't complete and was sent by mistake....
> >
> > R1's S0/0 is connected to R5's S0/0.1 and they have network address
> > 170.12.23.0/24 with IP Address 170.12.23.1 and 170.12.23.5.
> >
> > R5 has another S0/0.2 and have IP 173.23.23.5/24. On R1 you give default route
> >
> > ip route 0.0.0.0 0.0.0.0 serial 0/0
> >
> > Now as R5 has
> >
> > C 173.12.23.0 connected to S0/0
> > C 173.23.23.0 connected to S0/0
> >
> > in the Routing table and R 1 has defalut route to R5, if you say
> >
> > R1# ping 173.23.23.5
> >
> > Why R5 does not respond, when it has the entry for 173.23.23.5 in the
> > routing table and R1 is sending the packets with source IP
> > 173.12.23.1????
> > Because as I understand, R1 will send the packets for any destination
> > to R5, R5 shall look in to its RT that destination is 173.23.23.0, do
> > I know how to reach this network, Yes, it is directly connected, so it
> > shall respond, but its not, can any bosy explain why?
> >
> > Regards,
> >
> > Mohammad Zahed
> >
> > _______________________________________________________________________
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