From: Brian Dennis (bdennis@internetworkexpert.com)
Date: Sun Feb 04 2007 - 02:42:50 ART
<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 > > _______________________________________________________________________ > Subscription information may be found at: > http://www.groupstudy.com/list/CCIELab.html
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