I faced this problem several times...
http://www.cisco.com/warp/public/105/21.html
----------------------------------------------------------------------------
-----------------------------------
IP Classless
Where the ip classless configuration command falls within the routing and
forwarding processes is often confusing. In reality, IP classless only
effects the operation of the forwarding processes in IOS; it doesn't effect
the way the routing table is built. If IP classless isn't configured (using
the no ip classless command), the router won't forward packets to supernets.
As an example, let's again place three routes in the routing table and route
packets through the router.
router#show ip route
....
172.30.0.0/16 is variably subnetted, 2 subnets, 2 masks
D 172.30.32.0/20 [90/4879540] via 10.1.1.2
D 172.30.32.0/24 [90/25789217] via 10.1.1.1
S* 0.0.0.0/0 [1/0] via 10.1.1.3
Remembering that the 172.30.32.0/24 network includes the addresses
172.30.32.0 through 172.30.32.255, and the 172.30.32.0/20 network includes
the addresses 172.30.32.0 through 172.30.47.255, we can then try switching
three packets through this routing table and see what the results are.
A packet destined to 172.30.32.1 is forwarded to 10.1.1.1, since this is the
longest prefix match.
A packet destined to 172.30.33.1 is forwarded to 10.1.1.2, since this is the
longest prefix match.
A packet destined to 192.168.10.1 is forwarded to 10.1.1.3; since this
network doesn't exist in the routing table, this packet is forwarded to the
default route.
A packet destined to 172.30.254.1 is dropped.
The surprising answer out of these four is the last packet, which is
dropped. It's dropped because its destination, 172.30.254.1, is within a
known major network, 172.30.0.0/16, but the router doesn't know about this
particular subnet within that major network.
This is the essence of classful routing: If one part of a major network is
known, but the subnet toward which the packet is destined within that major
network is unknown, the packet is dropped.
----------------------------------------------------------------------------
---------------------------------------------------------------------------
-----Original Message-----
From: suaveguru [mailto:[EMAIL PROTECTED]]
Sent: Monday, January 29, 2001 11:40 AM
To: [EMAIL PROTECTED]
Subject: strange problem
hi I got a customer who intially has a defautl route
that does not work . Interesting is that when I take
out the statement and put in again it works perfect.
I am puzzled about such problem
ip classless is all the while in
customer is running 25xx series routers
any form of input will be greatly appreciated
regards,
suaveguru
__________________________________________________
Do You Yahoo!?
Yahoo! Auctions - Buy the things you want at great prices.
http://auctions.yahoo.com/
_________________________________
FAQ, list archives, and subscription info:
http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
_________________________________
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
