default routing

[riverfest]

I set an IP route of 0.0.0.0 0.0.0.0 172.16.20.1. I did NOT enter the ip classless command.

I am still able to ping all outside interfaces successfully and this router responds to all pings.

It was my understanding that I had to use the IP classless command for default routing so that the router would not drop packets, but forward them.
Any ideas why this appears contrary to what the book says?
( I am issuing these commands for default routing on a 3620 with IOS 12.3, but the other routers are 3640's with IOS 12.4)

Thanks,
Riverfest

[avinash]

ip classless command is enabled by default in Cisco IOS version 11.3 and later.
Perhaps this is reason the router is responding to ping.

Try again, after "no ip classless" in Global Config mode.

[lammle]

It is possible the ip classless command is not showing up in your configuration.
In my 2811 routers running 12.4, it does not, yet it is enabled.
Also, ironically, I have turned off the ip classes command on routers running 11.2 and it still worked about 50% of the time. Although Cisco's documentation says it would never work.
Cheers!
Todd Lammle

[riverfest]

Thank you all for your replies.

When I do a "show run" on each router, they all show a "no ip classless".

I have also found out that although each interface responds to pings, I cannot telnet into any other interface (except the adjoining directly connected one). If I try i receive a " % Destination unreachable; gateway or host down" error message.

I guess ICMP packets are treated differently than telnet packets. i am going to have to try and wrap my head around this one some more.

Thanks again,
Riverfest

[lammle]

A packet is a packet....

telet goes through TCP to get to IP, and ICMP sends payloads to IP, either way, everything goes through IP equally.

you have a routing problem. check your static or dynamic routing configurations.
Todd

[avinash]

A packet is a packet....

telet goes through UDP to get to IP, and ICMP sends payloads to IP, either way, everything goes through IP equally.

you have a routing problem. check your static or dynamic routing configurations.
Todd

I guess you meant, telnet goes through TCP...

Regards

A.

[lammle]

that's what I wrote! LOL

I edited my post....thanks.
Todd

[Tung Kelvin]

Dear Mr Todd!
I'm reading your CCNA Study Guide Book,i really appreciate your great work:D.And now i have a question just need your help.In chapter 6-Ip Routing,at the page of 374,you said as following:

"In the internetworking example used in the previous section,the only routers that are considered to be in a stub network are R1,R2,and the 871W.If you tried to put a default route on router R3,packets wouldn't be forwarded to the correct networks because they have more than one interface routing to other routers."

But i can't see any differences between R1,R2 and R3 .As we can see,R2 only has one exit path out of the network which is Serial Interface S0/2/0,as well as R3 only has one exit path out of the network which is Serial Interface S0/0/1.

Why R1,R2 are considered to be in a stub network whereas R3 is not?
Why can't I put a default route on R3?
Please talk more details about it!Thanks in advance!
http://img519.imageshack.us/img519/1959/figure69zc3.jpg

--Tung Kelvin--

[sikusantanu]

donno :(....i too need a reply regarding this....also...i want to know how the first review mcq has been answered....unable to understand