'no ip classless' not working?
tom
it break things I set 'no ip classless'. However, I am not getting the
result I expected and I was hoping someone could tell me what I'm
missing.
My lab topology is set up like so:
RouterA---10.32.20.0/24---RouterB---10.32.10.0/24---
RouterC---10.32.32.0/24---RouterD---10.35.35.0/24--->
RouterB is set with 'no ip classless' and its routing table is below:
RouterB#show ip route
Gateway of last resort is 10.32.10.254 to network 0.0.0.0
172.16.0.0/24 is subnetted, 1 subnets
C 172.16.30.0 is directly connected, FastEthernet0/1.30
10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
C 10.32.10.0/24 is directly connected, FastEthernet0/0.10
C 10.32.20.0/24 is directly connected, FastEthernet0/1.20
S 10.100.0.0/14 [1/0] via 10.32.10.254
S* 0.0.0.0/0 [1/0] via 10.32.10.254
If I understand how classful routing works, I should not be able to
ping 10.35.35.1 from RouterA; the reason being that RouterB is
configured for classful routing and has routes to other networks in
10.0.0.0/8 (but not 10.35.35.0/24). Therefore, RouterB discards the
packet.
However, when I try to ping 10.35.35.1, it works fine:
RouterA#ping 10.35.35.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.35.35.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/4 ms
RouterA#traceroute 10.35.35.1
Type escape sequence to abort.
Tracing the route to 10.35.35.1
1 10.32.20.253 0 msec 0 msec 0 msec
2 10.32.10.254 4 msec 4 msec 0 msec
3 10.35.35.1 4 msec 8 msec 0 msec
alexd
> I am playing with some routers in a lab and just to say that I've seen
> it break things I set 'no ip classless'.
What IOS are you using? I'm sure I heard that classful support has been
dropped from recent IOS, but I can't find a reference to it at the moment.
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<181e9c7c-b772-4e4c...@k30g2000yqf.googlegroups.com> tom
wrote:
Is it possible that a router on 10.32.20.X is doing proxy ARP?
jrg...@gmail.com
> In the message
> <181e9c7c-b772-4e4c-8130-eb840332e...@k30g2000yqf.googlegroups.com> tom
routing.. You will notice that if any part of the destination IP
addresses classful network is in the routing table, the router will
not use the default route to forward the packet. I would suggest
trying this with dynamic routing protocols (RIPv2, EIGRP, etc..) to
test behavior also.
tom
>
> What IOS are you using? I'm sure I heard that classful support has been
> dropped from recent IOS, but I can't find a reference to it at the moment.
The routers are all running 12.3 or 12.4 (details below). Regarding
Proxy ARP, I don't think it is configured, I certainly didn't
configure it explicitly. The A-C configs are below. Thanks for the
suggestions.
RouterA is a 1720 running 12.3(23)
RouterB is a 1841 running IP Base 12.3(8)T5
RouterC is a 3640 running IP Plus 12.4(16)
RouterD is actually a Pix501 running 6.3.5
==RouterA config==
version 12.3
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname c1700
!
boot-start-marker
boot-end-marker
!
no logging buffered
enable secret 5 $1$aGun$pr7FjqTJLRWJr7IK7ZybZ/
!
memory-size iomem 25
no aaa new-model
ip subnet-zero
!
no ip domain lookup
!
ip cef
!
interface FastEthernet0
ip address 10.32.20.20 255.255.255.0
speed auto
!
interface Serial0
no ip address
shutdown
!
ip classless
ip default-network 10.0.0.0
ip route 0.0.0.0 0.0.0.0 172.16.30.253
ip route 0.0.0.0 0.0.0.0 10.32.20.253
ip route 10.32.10.0 255.255.255.0 10.32.20.253
ip route 10.32.10.0 255.255.255.0 172.16.30.253
no ip http server
!
line con 0
exec-timeout 0 0
logging synchronous
line aux 0
line vty 0 4
exec-timeout 0 0
password cisco
logging synchronous
login
==RouterB config==
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname 1841
!
boot-start-marker
boot-end-marker
!
enable secret 5 $1$hiFe$mTnPJtBBtct5FO6c8D/Dp0
!
username cisco secret 5 $1$f6gj$PjxDNivBCz/JtXQZbi7w3.
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
no aaa new-model
ip subnet-zero
ip cef
!
!
!
!
no ip domain lookup
no ftp-server write-enable
!
!
!
!
interface FastEthernet0/0
no ip address
duplex auto
speed auto
!
interface FastEthernet0/0.10
encapsulation dot1Q 10
ip address 10.32.10.253 255.255.255.0
no cdp enable
!
interface FastEthernet0/0.20
!
interface FastEthernet0/1
no ip address
duplex auto
speed auto
!
interface FastEthernet0/1.20
encapsulation dot1Q 20
ip address 10.32.20.253 255.255.255.0
!
interface FastEthernet0/1.30
encapsulation dot1Q 30 native
ip address 172.16.30.253 255.255.255.0
!
interface Serial0/0/0
no ip address
shutdown
!
no ip classless
ip route 0.0.0.0 0.0.0.0 10.32.10.254
ip route 10.100.0.0 255.252.0.0 10.32.10.254
no ip http server
!
!
!
control-plane
!
!
line con 0
exec-timeout 0 0
logging synchronous
history size 15
line aux 0
line vty 0 4
exec-timeout 0 0
logging synchronous
login local
history size 15
line vty 5 15
exec-timeout 0 0
logging synchronous
login local
history size 15
==RouterC config==
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname r2
!
boot-start-marker
boot-end-marker
!
enable secret 5 $1$Z7iL$d6iyr1T0G5GGJIBeEB5IX1
!
no aaa new-model
!
ip cef
no ip domain lookup
!
username cisco secret 5 $1$xFnX$32qbiWsFGoGCIWrmPURPO.
!
interface FastEthernet0/0
no ip address
duplex auto
speed auto
!
interface FastEthernet0/0.1
encapsulation isl 1
ip address 10.32.32.254 255.255.255.0
no ip redirects
!
interface FastEthernet0/0.10
encapsulation isl 10
ip address 10.32.10.254 255.255.255.0
no ip redirects
!
interface Serial0/0
no ip address
shutdown
!
interface Serial0/1
no ip address
shutdown
clock rate 2000000
!
interface Serial0/2
no ip address
shutdown
!
ip http server
!
no ip classless
ip route 0.0.0.0 0.0.0.0 10.32.32.1
ip route 10.32.20.0 255.255.255.0 10.32.10.253
ip route 172.16.30.0 255.255.255.0 10.32.10.253
!
control-plane
!
line con 0
exec-timeout 0 0
logging synchronous
line aux 0
line vty 0 4
exec-timeout 0 0
logging synchronous
login local
line vty 5 15
exec-timeout 0 0
logging synchronous
login local
Thrill5
that or its broken. I do know that classless routing is now the default in
the newer versions of IOS, I'm not sure what version this changed. If it
were broken, I doubt that Cisco would fix it because the entire concept of
classfull routing was itself sent to the bit bucket more than 15 years ago.
A workaround is to add a static route for 10/8 to null0. This is exactly
what "no ip classless" would do anyway.
ip route 10.0.0.0 255.0.0.0 null0
"alexd" <trof...@hotmail.com> wrote in message
news:5196637.N...@ale.cx...
tom
> I'm pretty sure classfull routing is no longer supported as well, either
> that or its broken. I do know that classless routing is now the default in
> the newer versions of IOS, I'm not sure what version this changed. If it
> were broken, I doubt that Cisco would fix it because the entire concept of
> classfull routing was itself sent to the bit bucket more than 15 years ago.
> A workaround is to add a static route for 10/8 to null0. This is exactly
> what "no ip classless" would do anyway.
I don't doubt that the functionality was eliminated; it seems
prehistoric, and I've been trying to think of a situation in which it
would be useful. But if it is indeed depreciated, i wonder why it
would even still be a configuration option. Furthermore, I wonder why
it would still be included in the CCNA material, other than as a "this
is how things were in the bad old days" aside.
alexd
> But if it is indeed depreciated, i wonder why it
> would even still be a configuration option.
You'd hope the CLI would warn you if you tried to configure it, if it is
indeed now non-functional. It could of course just be a bug.
> Furthermore, I wonder why it would still be included in the CCNA material,
> other than as a "this is how things were in the bad old days" aside.
Indeed. My CCNA tutor seemed to think that serial interfaces were what made
the world go round.
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