no ip classless
jezg76
Member Posts: 97 ■■□□□□□□□□
in CCNA & CCENT
Greetings all! Question for the masses.
I am using Dynamips with 7200 model "routers". I am just going through the whole default route, default-network, classless routing, classful routing thing and am having an issue.
I have 4 routers in the following config...
Forgive my beautiful drawing.
R1 has 2 serial connections to the Corp router. There is a single serial connection between R2 and R3, respectively.
I have nothing but static routes for the routing between the routers using the following networks (except R3, the problem child...):
10.1.1.0 LAN Connection off Corp
10.1.2.0 1st Serial Connection between Corp and R1
10.1.3.0 2nd Serial Connection between Corp and R2
10.1.4.0 Serial Connection between Corp and R2
10.1.5.0 Serial Connection between Corp and R3
10.1.6.0 LAN Connection off R1
10.1.7.0 LAN Connection off R2
10.1.8.0 LAN Connection off R3
R3 has the following directly connected networks:
10.1.5.0 and 10.1.8.0.
Instead of doing static routes for this I decided to bust out the default route for this. The show ip route command gives the following output:
Sorry, this is soon over.
Next, just to solidify my understanding of classful vs. classless, I do the no ip classless global configuration command on R3. Then I do a ping 10.1.1.1, fully expecting it to not succeed, which would coincide with my readings.
Long story short, it succeeds. I just don't understand why. Classful routing should look at the 10.1.1.0 network, and, seeing that it is an unknown subnet in the major network 10.0.0.0, discard the packet to that network. Am I missing something in my understanding of classful vs. classless routing? Thanks in advance!
I am using Dynamips with 7200 model "routers". I am just going through the whole default route, default-network, classless routing, classful routing thing and am having an issue.
I have 4 routers in the following config...
____________R2
Corp|
______________| ||________________R3
R1-|--------------|
Forgive my beautiful drawing.
R1 has 2 serial connections to the Corp router. There is a single serial connection between R2 and R3, respectively.
I have nothing but static routes for the routing between the routers using the following networks (except R3, the problem child...):
10.1.1.0 LAN Connection off Corp
10.1.2.0 1st Serial Connection between Corp and R1
10.1.3.0 2nd Serial Connection between Corp and R2
10.1.4.0 Serial Connection between Corp and R2
10.1.5.0 Serial Connection between Corp and R3
10.1.6.0 LAN Connection off R1
10.1.7.0 LAN Connection off R2
10.1.8.0 LAN Connection off R3
R3 has the following directly connected networks:
10.1.5.0 and 10.1.8.0.
Instead of doing static routes for this I decided to bust out the default route for this. The show ip route command gives the following output:
Gateway of last resort is 10.1.5.1 to network 0.0.0.0
10.0.0.0/24 is subnetted, 2 subnets
C 10.1.8.0 is directly connected, FastEthernet0/0
C 10.1.5.0 is directly connected, Srial1/0
S* 0.0.0.0/0 [1/0] via 10.1.5.1
Sorry, this is soon over.
Next, just to solidify my understanding of classful vs. classless, I do the no ip classless global configuration command on R3. Then I do a ping 10.1.1.1, fully expecting it to not succeed, which would coincide with my readings.Long story short, it succeeds. I just don't understand why. Classful routing should look at the 10.1.1.0 network, and, seeing that it is an unknown subnet in the major network 10.0.0.0, discard the packet to that network. Am I missing something in my understanding of classful vs. classless routing? Thanks in advance!
policy-map type inspect TACO
class type inspect BELL
drop log
class type inspect BELL
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Comments
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Mikdilly
Member Posts: 309
I duplicated your setup in dynamips to the equivalent of your core router and R3.
R3#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is 10.1.5.1 to network 0.0.0.0
10.0.0.0/30 is subnetted, 1 subnets
C 10.1.5.0 is directly connected, Serial1/1
S* 0.0.0.0/0 [1/0] via 10.1.5.1
core#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
* 10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.1.1.0/24 is directly connected, FastEthernet0/1
C 10.1.5.0/30 is directly connected, Serial1/1
Turn off ip classless on R3
R3(config)#no ip classless
Ping 10.1.1.1
R3#ping 10.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.1, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
Ping fails as expected,
Turn on ip classless on R3
R3(config)#ip classless
Ping 10.1.1.1
R3#ping 10.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 12/25/40 ms
Maybe you should do a show run on R3 and verify that ip classless is turned off. -
jezg76
Member Posts: 97 ■■□□□□□□□□
Thanks for the response mikdilly. I am 100% certain I am using the no ip classless command.
I tried recreating it a much simpler lab with only two routers and it still is pinging with no ip classless enabled.
Very strange, indeed. I'll just chalk that up to not being able to use real equips.
Thanks for your help.[/i]policy-map type inspect TACO
class type inspect BELL
drop log