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Home > Archive > CCNA > April 2002 > Ron's QoTD
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| rsteedma 2002-04-19, 6:14 pm |
| You recently attached your router to a new subnet, 18.5.1.0/24. Which single command would tell RIPv1 to begin advertising the new subnet?
A. router(config-router)# network 18.0.0.0
B. router(config-router)# network 18.5.1.0
C. router(config-router)# network 18.5.1.0/24
D. router(config-router)# network 18.5.1.0 255.255.255.0
E. router(config-router)# router rip 18.5.1.0
F. None of the Above
-- Good Luck! --
Cheers,
Ron
---
Ron Steedman CCNP, CCNA, MCP, BS Computer Science
Free CCNA Practice Tests, Study Guides, & Message Boards!
http://www.congonetworking.com/ | |
| Tekwannabe 2002-04-19, 6:17 pm |
| That would be B | |
| ValleyBall1 2002-04-19, 6:25 pm |
| "B too..." | |
| Yeti-GBR1 2002-04-19, 6:33 pm |
| B. router(config-router)# network 18.5.1.0 | |
| rsteedma 2002-04-19, 6:43 pm |
| B is not the right answer...
Can someone provide the right answer AND why B is incorrect? 
---
Ron Steedman CCNP, CCNA, MCP, BS Computer Science
Free CCNA Practice Tests, Study Guides, & Message Boards!
http://www.congonetworking.com/ | |
| Yeti-GBR1 2002-04-19, 7:27 pm |
| Hmmm odd here is the config from my R1 router (its a 2524) and it works!!!!
------------------------------------
R1#sh run
Building configuration...
Current configuration : 515 bytes
!
version 12.2 <--- may be this that makes it work though
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname R1
!
!
ip subnet-zero
!
!
!
!
interface Ethernet0
ip address 192.168.0.1 255.255.255.0
!
interface Serial0
no ip address
shutdown
!
interface Serial1
no ip address
shutdown
!
interface BRI0
no ip address
shutdown
!
router rip
network 192.168.0.0
!
ip classless
ip http server
ip pim bidir-enable
!
!
!
line con 0
logging synchronous
line aux 0
line vty 0 4
password cisco
login
!
end
R1#sh ip route
Codes: C - connected, S - static, I - IGRP, 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, E - EGP
i - IS-IS, 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
C 192.168.0.0/24 is directly connected, Ethernet0
R1#sh ip rip database
192.168.0.0/24 auto-summary
192.168.0.0/24 directly connected, Ethernet0
R1#
------------------------------------
Ron please do explain why you think/know it to be wrong then  | |
| Yeti-GBR1 2002-04-19, 7:38 pm |
| Unless your refering to this:
To get the command line to this point from the 1st screen use the following:
router>enable <enter password as requested>
router#configure terminal
router(config)#router rip <places it in router mode & activates RIP V1>
router(config-router)# network 18.5.1.0
router(config-router)#exit
router(config)#exit
router#
the above assumes that you have done the following beforehand though:
router#configure terminal
router(config)#interface ethernet 0<places you in interface ethernet0>
router(config-inf)#ip address 18.5.1.0 255.255.255.0
router(config-inf)#no shutdown < enable ethernet port 0>
router(config-inf)#exit
router(config)#exit
Hmm may be you know something ath I/we do not...is somthing missing from the question | |
| Yeti-GBR1 2002-04-19, 7:40 pm |
| And if your refering to it being a ZERO subnet...tough in IOS 12.1 there allowed | |
| Yeti-GBR1 2002-04-19, 7:44 pm |
| Bingo...(did you hear the penny drop?)
R1(config)#int e0
R1(config-if)#ip add 18.5.1.0 255.255.255.0
Bad mask /24 for address 18.5.1.0
R1(config-if)#
Dhooooooo...nice one Ron
Correct Answer is F  | |
| Yankee 2002-04-19, 7:46 pm |
| Sorry, but the question said RIP version 1 so he wants the answer A, I would think. A classful routing protocol...
Yankee | |
| Yeti-GBR1 2002-04-19, 7:54 pm |
| Cough.....
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#no ip classless
R1(config)#int e0
R1(config-if)#ip add 18.5.1.0 255.255.255.0
Bad mask /24 for address 18.5.1.0
R1(config-if)#
R1#sh ip prot
Routing Protocol is "rip"
Sending updates every 30 seconds, next due in 4 seconds
Invalid after 180 seconds, hold down 180, flushed after 240
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Redistributing: rip
Default version control: send version 1, receive any version
Interface Send Recv Triggered RIP Key-chain
Ethernet0 1 1 2
Automatic network summarization is in effect
Maximum path: 4
Routing for Networks:
192.168.0.0
Routing Information Sources:
Gateway Distance Last Update
Distance: (default is 120)
R1#
Don't think so  Soz Yankee unless I have lost the plot completley..it is 01:50 here in the UK 
Even if you do the following still does not allow it:
R1(config-router)#no auto-summary
R1(config-router)#ver 1
R1(config-router)#int e0
R1(config-if)#ip add 18.5.1.0 255.255.255.0
Bad mask /24 for address 18.5.1.0
R1(config-if)# | |
| Yankee 2002-04-19, 9:32 pm |
| Version 1 is classful so you need the network stated as a class A address. The other problem you show with the bad subnet mask response is because you need "ip subnet-zero" statement added.
Yankee | |
| Yeti-GBR1 2002-04-19, 9:44 pm |
| knew I was up too late this morning...cheers Yankee.  | |
|
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| Yeti-GBR1 2002-04-19, 9:53 pm |
| Having had a coffee & several cigs and re-read the question I now seeeeeeee the light!!! its Sooooo obvious...
18.0.0.0 Dam I'm an Idiot...yip A is the answer..not B-F
Since RIP V1 only sees the A, B & C classes (ie Classful).
R1(config-if)#ip add 18.5.1.1 255.255.255.0
R1(config-if)#router rip
R1(config-router)#exi
R1(config)#ip classless
R1(config)#router rip
R1(config-router)#net 18.0.0.0
R1(config-router)#
R1#
3d05h: %SYS-5-CONFIG_I: Configured from console by console
R1#sh ip route
Codes: C - connected, S - static, I - IGRP, 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, E - EGP
i - IS-IS, 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
18.0.0.0/24 is subnetted, 1 subnets
C 18.5.1.0 is directly connected, Ethernet0
R1# | |
| rsteedma 2002-04-19, 11:57 pm |
| Right on Yankee and Yeti!!! The correct answer is A, "network 10.0.0.0"!
RIPv1 is a classful network protocol - it doesn't send a subnet mask in its updates.
When configuring RIPv1, remember to specify the classful network number, not the subnet number.
You can find a good overview of RIPv1 at the following website:
http://netcert.tripod.com/ccna/routers/rip.html
About the "ip subnet-zero" command: It allows you to use the all-zeroes subnet address, not the all-zeroes host address.
Here's an example of what it does and doesn't allow:
router(config)#int loo0
router(config-if)#ip add 12.0.0.1 255.255.0.0
Bad mask /16 for address 12.0.0.1
router(config-if)#ip subnet-zero
router(config)#int loo0
router(config-if)#ip add 12.0.0.1 255.255.0.0
router(config-if)#ip add 12.0.0.0 255.255.0.0
Bad mask /16 for address 12.0.0.0
router(config-if)#
Thanks,
Ron
---
Ron Steedman CCNP, CCNA, MCP, BS Computer Science
Free CCNA Practice Tests, Study Guides, & Message Boards!
http://www.congonetworking.com/ | |
| marathoner 2002-04-20, 2:00 am |
| quote:
Originally posted by Yankee
Sorry, but the question said RIP version 1 so he wants the answer A, I would think. A classful routing protocol...
Yankee
I think you're on the right track, but it can't be A if you really have a /24 going. | |
| rsteedma 2002-04-20, 2:28 am |
| It really does work that way. It's tricky!
Here's another scenario:
A router is connected to subnets:
130.10.62.0/24
130.10.63.0/24
130.10.8.0/24
130.10.9.0/24
The RIP configuration is:
router rip
network 130.10.0.0
You can see this in action by visiting the link below and clicking on "Configuring RIP".
http://www.cisco.com/univercd/cc/td...k/ics/cs001.htm
---
Ron Steedman CCNP, CCNA, MCP, BS Computer Science
Free CCNA Practice Tests, Study Guides, & Message Boards!
www.congonetworking.com/ | |
|
| Good question, but I don't think enough info was given in the question which Marothoner was on the way to saying.
With Rip v1 you can amend the subnet mask, i.e. 10.1.1.0/24 and as long as you use this mask throughout your network your OK.
Look at this link:
http://www.cisco.com/warp/public/105/53.html
As you can see from the link theyre mixing the class B addresses with /30 and /24 with the /24 being dropped.
I would say the answer is a or b - depending on on the network mask currently used on yuor network - information not given in the question. | |
| rsteedma 2002-04-20, 1:14 pm |
| Hi MattP,
You brought up a great point!
I do enjoy a good technical discussion. And that's a good Cisco link to check out.
RIP Advertisements:
------------------
RIPv1 advertises subnet 18.5.1.0 when it's advertising within the 18.0.0.0 network. All routers in a RIPv1 network must us the same subnet mask, so this works well.
RIPv1 advertises network 18.0.0.0 whn it's advertising outside the 18.0.0.0. The is a forced summarization at classful boundaries.
RIPv1 Configuration:
-------------------
You always use "network <classful-network>".
The router would reject answers C, D, & E:
router(config-router)# network 18.5.1.0/24
router(config-router)# network 18.5.1.0 255.255.255.0
router(config-router)# router rip 18.5.1.0
The router would happily accept answer A:
router(config-router)# network 18.0.0.0
The router automatically corrects answer B into answer A if you attempt to enter it:
router(config-router)#network 18.5.1.0
router(config-router)#end
router#sh run
...
router rip
network 18.0.0.0
!
...
The router considers answer A the only valid configuration command.
Cheers,
Ron
---
Ron Steedman CCNP, CCNA, MCP, BS Computer Science
Free CCNA Practice Tests, Study Guides, & Message Boards!
www.congonetworking.com/ | |
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| Yeti-GBR1 2002-04-20, 1:25 pm |
| One could suppose that the correct answers should then be A & B since:
quote:
The router would happily accept answer A:
router(config-router)# network 18.0.0.0
The router automatically corrects answer B into answer A if you attempt to enter it:
router(config-router)#network 18.5.1.0
router(config-router)#end
router#sh run
...
router rip
network 18.0.0.0
!
...
Man this just gets better ... | |
| rsteedma 2002-04-20, 3:40 pm |
| Haha!
I totally buy that one, Yeti.
Seriously. A, A&B, and B are all good answers as long we understand what they do!
For example: "network 18.5.1.0" is translated to "network 18.0.0.0" which advertises all the subnets on the 18.0.0.0 network, not just subnet 18.5.1.0.
I hope readers will come away from our thread with a deeper grasp of RIPv1:
1. "network 18.0.0.0" vs "network 18.5.1.0".
2. RIPv1 can handle subnets, but not VLSM.
3. The effect of the command "ip subnet-zero".
Cheers,
Ron
---
Ron Steedman CCNP, CCNA, MCP, BS Computer Science
Free CCNA Practice Tests, Study Guides, & Message Boards!
www.congonetworking.com/ | |
| Yeti-GBR1 2002-04-20, 6:13 pm |
| Ok Ron Agreed Next brain buster please | |
| Yankee 2002-04-22, 8:05 am |
| What the router advertises and how you config router RIP are two different issues. Matt's correct about the advertisements but the question asked was more basic. Be careful not to read too much into a question and confuse yourself from what it is actually asking. Just because the router corrects your error it doesn't mean you have typed in the proper syntax. In fact it means the opposite...that you were wrong and the router was smart enough to make it right, thus B can not be considered a correct answer.
Guess we have beat this one to death
Yankee | |
| tuckerca 2002-04-22, 10:51 pm |
| the answer is A Rip v1 only works for classfull ip[ address |
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