I need help with a lab problem

Hello:

I have 3 routers and they are all connected via serial cables. RouterA is connected to RouterB and RouterC is connected to RouerB via serial cables. Each router has a transceiver to convert the AUI to Ethernet using 2501 Series routers. I have setup all the interfaces and all interfaces are up. I have setup routing using RIP. The lab is setup as the following:

RouterA
Serial 0 - IP address 192.168.1.1 255.255.255.0
Ethernet 0 - IP address 10.1.1.1 255.0.0.0
LAN Host - IP address 10.1.1.2 255.0.0.0, gway 10.1.1.1
I have advertised both of these networks with RIP.

RouterB
Serial 1 - IP address 192.168.1.2 255.255.255.0
Ethernet 0 IP address 172.16.1.1 255.255.0.0
LAN Host - Ip address 172.16.1.2 255.255.0.0, gway 172.16.1.1

RouterC
Serial 0 - IP address 68.1.1.1 255.0.0.0
Ethernet 0 - IP address 72.1.1.1 255.0.0.0
LAN Host - IP address 72.1.1.2 255.0.0.0, gway 72.1.1.1

I disconnected my hosts from the Internet. I applied the default subnet masks. All Routers are converged. I can ping from 72.1.1.1 to 192.168.1.1, but I cannot ping the host IP addresses. Any ideas? I hope this makes sense.

I dont have a picture of my routing tables.

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Comments

shednik

Well lets see there could be different reasons why you are having trouble...

To fully be able to tell I'd need to see your running configs...

Also have you tried a tracert to see where the failure point is...

Try that first let us know and let us get a look at your configs

markzab

You can copy and paste the routing table from hyperterminal. Or are you connected to the routers via a different PC than the one you're using to write to us?

Going to be a bit hard to help without being able to see configs or any other outputs.

I guess a good place to start would be to ask you if from your hosts you can ping the default gateways? If so then go up one level and then try to ping your serial interface from the host. Then if that works try to ping the serial of the next hop router from the host. Let us know where you run into your first problem.

vjsousa

When I get home than I will copy and paste the running-config and routing tables.

shednik

Sounds good, try the tests as well

tech-airman

vjsousa wrote:

Hello:

I have 3 routers and they are all connected via serial cables. RouterA is connected to RouterB and RouterC is connected to RouerB via serial cables. Each router has a transceiver to convert the AUI to Ethernet using 2501 Series routers. I have setup all the interfaces and all interfaces are up. I have setup routing using RIP. The lab is setup as the following:

RouterA
Serial 0 - IP address 192.168.1.1 255.255.255.0
Ethernet 0 - IP address 10.1.1.1 255.0.0.0
LAN Host - IP address 10.1.1.2 255.0.0.0, gway 10.1.1.1
I have advertised both of these networks with RIP.

RouterB
Serial 1 - IP address 192.168.1.2 255.255.255.0
Ethernet 0 IP address 172.16.1.1 255.255.0.0
LAN Host - Ip address 172.16.1.2 255.255.0.0, gway 172.16.1.1

RouterC
Serial 0 - IP address 68.1.1.1 255.0.0.0
Ethernet 0 - IP address 72.1.1.1 255.0.0.0
LAN Host - IP address 72.1.1.2 255.0.0.0, gway 72.1.1.1

I disconnected my hosts from the Internet. I applied the default subnet masks. All Routers are converged. I can ping from 72.1.1.1 to 192.168.1.1, but I cannot ping the host IP addresses. Any ideas? I hope this makes sense.

I dont have a picture of my routing tables.

vjsousa,

You state that "RouterA is connected to RouterB and RouterC is connected to RouerB via serial cables." yet RouterB only has a single "Serial 1" interface configured with an IP address and subnet mask. Based on the IP address of the Serial 0 interface of RouterA and the IP address of the Serial 1 interface of RouterB, it seems like your statement "RouterA is connected to RouterB " may be correct. However, I find it inconsistent that you state "RouterC is connected to RouerB via serial cables" and "I can ping from 72.1.1.1 to 192.168.1.1" when there is no serial interface on RouterB configured with an IP address in the 68.0.0.0 network, excluding 68.1.1.1 because that is assigned to the Serial 0 interface of RouterC and excluding 68.255.255.255 because that is the broadcast address for that network.

As Johnny Five in "Short Circuit" said, "Need more input."

Netstudent

Ya that topology and IP scheme doesn't make sense. you have a dead end there buddy. From that info. theres no way that C could get to B, much less C getting to A. Double check your topology because something is missing.

vjsousa

All interfaces are up. I apologize, but Serial 0 on RouterB is connected to Serial 0 on RouterC. The NIC's are set to AUTO/AUTO.

tech-airman

vjsousa wrote:

All interfaces are up. I apologize, but Serial 0 on RouterB is connected to Serial 0 on RouterC. The NIC's are set to AUTO/AUTO.

vjsousa,

What IP address and subnet mask did you configure on the Serial 0 interface of RouterB?

vjsousa

Im doing this off of memory, so forgive me if I forget. I will copy and paste the running-configs and routing tables.

tech-airman

vjsousa wrote:

Im doing this off of memory, so forgive me if I forget. I will copy and paste the running-configs and routing tables.

vjsousa,

You mentioned "I can ping from 72.1.1.1 to 192.168.1.1, but I cannot ping the host IP addresses." Since 72.1.1.1 is the IP address assigned to the Ethernet 0 interface of RouterC, I'm assuming you were pinging from within the router through a terminal connected to the console port. How did you determine "I cannot ping the host IP addresses?" Did you see "....." instead of "!!!!!"?

Also, I noticed that RouterA and RouterB have valid private IP addresses, however RouterC has some public IP addresses. According to RFC 1918 - Address Allocation for Private Internets, it states...

RFC 1918 - Address Allocation for Private Internets wrote:

Because private addresses have no global meaning, routing information
about private networks shall not be propagated on inter-enterprise
links, and packets with private source or destination addresses
should not be forwarded across such links. Routers in networks not
using private address space, especially those of Internet service
providers, are expected to be configured to reject (filter out)
routing information about private networks. If such a router receives
such information the rejection shall not be treated as a routing
protocol error.

So you do you have Network Address Translation configured on RouterB to communicate between the private IP sub/networks on RouterA and RouterB with the public IP network on RouterC? If so, then I'm curious to know how you were able to "ping from 72.1.1.1 to 192.168.1.1" which would be from NAT outside to NAT inside when from what I know of NAT, filters packets that were initiated from the outside trying to go inside.

Source:

RFC 1918 - Address Allocation for Private Internets - http://www.ietf.org/rfc/rfc1918.txt?number=1918

vjsousa

No NAT. You might be right about the routing of public IP addresses. I will copy the run-config when I get home tonight.

Netstudent

tech-airman wrote:

vjsousa wrote:

Im doing this off of memory, so forgive me if I forget. I will copy and paste the running-configs and routing tables.

vjsousa,

You mentioned "I can ping from 72.1.1.1 to 192.168.1.1, but I cannot ping the host IP addresses." Since 72.1.1.1 is the IP address assigned to the Ethernet 0 interface of RouterC, I'm assuming you were pinging from within the router through a terminal connected to the console port. How did you determine "I cannot ping the host IP addresses?" Did you see "....." instead of "!!!!!"?

Also, I noticed that RouterA and RouterB have valid private IP addresses, however RouterC has some public IP addresses. According to RFC 1918 - Address Allocation for Private Internets, it states...

RFC 1918 - Address Allocation for Private Internets wrote:

Because private addresses have no global meaning, routing information
about private networks shall not be propagated on inter-enterprise
links, and packets with private source or destination addresses
should not be forwarded across such links. Routers in networks not
using private address space, especially those of Internet service
providers, are expected to be configured to reject (filter out)
routing information about private networks. If such a router receives
such information the rejection shall not be treated as a routing
protocol error.

So you do you have Network Address Translation configured on RouterB to communicate between the private IP sub/networks on RouterA and RouterB with the public IP network on RouterC? If so, then I'm curious to know how you were able to "ping from 72.1.1.1 to 192.168.1.1" which would be from NAT outside to NAT inside when from what I know of NAT, filters packets that were initiated from the outside trying to go inside.

Source:
RFC 1918 - Address Allocation for Private Internets - http://www.ietf.org/rfc/rfc1918.txt?number=1918

RFC 1918 is only for public networks. Not for a personal lab with back to back connections. As long as he is using the same subnet mask for each Network and using contiguous networks that shouldn't matter. Double check your rip configuration and make sure you have a route to routerA's ethernet interface from router C.

vjsousa

I will post the routing tables and running-config to this forum and any help would be appreciated.

georgemc

Netstudent wrote:

tech-airman wrote:

vjsousa wrote:

Im doing this off of memory, so forgive me if I forget. I will copy and paste the running-configs and routing tables.

vjsousa,

You mentioned "I can ping from 72.1.1.1 to 192.168.1.1, but I cannot ping the host IP addresses." Since 72.1.1.1 is the IP address assigned to the Ethernet 0 interface of RouterC, I'm assuming you were pinging from within the router through a terminal connected to the console port. How did you determine "I cannot ping the host IP addresses?" Did you see "....." instead of "!!!!!"?

Also, I noticed that RouterA and RouterB have valid private IP addresses, however RouterC has some public IP addresses. According to RFC 1918 - Address Allocation for Private Internets, it states...

RFC 1918 - Address Allocation for Private Internets wrote:

Because private addresses have no global meaning, routing information
about private networks shall not be propagated on inter-enterprise
links, and packets with private source or destination addresses
should not be forwarded across such links. Routers in networks not
using private address space, especially those of Internet service
providers, are expected to be configured to reject (filter out)
routing information about private networks. If such a router receives
such information the rejection shall not be treated as a routing
protocol error.

So you do you have Network Address Translation configured on RouterB to communicate between the private IP sub/networks on RouterA and RouterB with the public IP network on RouterC? If so, then I'm curious to know how you were able to "ping from 72.1.1.1 to 192.168.1.1" which would be from NAT outside to NAT inside when from what I know of NAT, filters packets that were initiated from the outside trying to go inside.

Source:
RFC 1918 - Address Allocation for Private Internets - http://www.ietf.org/rfc/rfc1918.txt?number=1918

RFC 1918 is only for public networks. Not for a personal lab with back to back connections. As long as he is using the same subnet mask for each Network and using contiguous networks that shouldn't matter. Double check your rip configuration and make sure you have a route to routerA's ethernet interface from router C.

Thank you....

Cucumber

It is important to read the standards having in mind the difference between the words "can", "may", "should", etc.
Actually at the begining of all the standards the difference between these words is stressed on.

For instance, in the quote:
"packets with private source or destination addresses should not be forwarded across such links"

This means packets CAN be forwarded but SHOULD not (over the Internet). There is no inherent filtering on any router that would stop packets having private addresses as source or destination from being forwarded.

Netstudent

Ya...it's more like a methodology rather than something that is hardcoded into the IOS.

tech-airman

Netstudent wrote:

tech-airman wrote:

vjsousa wrote:

Im doing this off of memory, so forgive me if I forget. I will copy and paste the running-configs and routing tables.

vjsousa,

You mentioned "I can ping from 72.1.1.1 to 192.168.1.1, but I cannot ping the host IP addresses." Since 72.1.1.1 is the IP address assigned to the Ethernet 0 interface of RouterC, I'm assuming you were pinging from within the router through a terminal connected to the console port. How did you determine "I cannot ping the host IP addresses?" Did you see "....." instead of "!!!!!"?

Also, I noticed that RouterA and RouterB have valid private IP addresses, however RouterC has some public IP addresses. According to RFC 1918 - Address Allocation for Private Internets, it states...

RFC 1918 - Address Allocation for Private Internets wrote:

Because private addresses have no global meaning, routing information
about private networks shall not be propagated on inter-enterprise
links, and packets with private source or destination addresses
should not be forwarded across such links. Routers in networks not
using private address space, especially those of Internet service
providers, are expected to be configured to reject (filter out)
routing information about private networks. If such a router receives
such information the rejection shall not be treated as a routing
protocol error.

So you do you have Network Address Translation configured on RouterB to communicate between the private IP sub/networks on RouterA and RouterB with the public IP network on RouterC? If so, then I'm curious to know how you were able to "ping from 72.1.1.1 to 192.168.1.1" which would be from NAT outside to NAT inside when from what I know of NAT, filters packets that were initiated from the outside trying to go inside.

Source:
RFC 1918 - Address Allocation for Private Internets - http://www.ietf.org/rfc/rfc1918.txt?number=1918

RFC 1918 is only for public networks. Not for a personal lab with back to back connections. As long as he is using the same subnet mask for each Network and using contiguous networks that shouldn't matter. Double check your rip configuration and make sure you have a route to routerA's ethernet interface from router C.

According to "IP Address Lookup (IPv4 & IPv6)", the network address range of 68.0.0.0 through 68.15.255.255 is owned by Cox Communications. The network address range of 72.0.0.0 through 72.0.31.255 is owned by "CITISTREET." I don't believe that valid IP addresses, especially valid ones owned by organizations belong in a "personal lab with back to back connections."

IP Address Lookup (IPv4 & IPv6) - 68.0.0.0 wrote:

IP owner info (Whois)Cox Communications Inc. COX-ATLANTA (NET-68-0-0-0-1) 68.0.0.0 - 68.15.255.255Cox Communications Inc. AT-68-0-0-0 (NET-68-0-0-0-2) 68.0.0.0 - 68.0.15.255 # ARIN WHOIS database, last updated 2007-05-29 19:10# Enter ? for additional hints on searching ARIN's WHOIS database.

IP Address Lookup (IPv4 & IPv6) - 72.0.0.0 wrote:

IP owner info (Whois)OrgName: CITISTREET OrgID: CITIST-2Address: 3 Pinehill DriveCity: QuincyStateProv: MAPostalCode: 02169Country: US NetRange: 72.0.0.0 - 72.0.31.255 CIDR: 72.0.0.0/19 NetName: CITISTREET-ENTERPRISENetHandle: NET-72-0-0-0-1Parent: NET-72-0-0-0-0NetType: Direct AssignmentNameServer: HLPNS001.CITISTREET.NETNameServer: HLPNS501.CITISTREET.NETComment: RegDate: 2004-09-10Updated: 2004-09-10 OrgTechHandle: PCO25-ARINOrgTechName: Coughlin, Patrick OrgTechPhone: +1-617-376-9012OrgTechEmail: pcoughlin@citistreetonline.com # ARIN WHOIS database, last updated 2007-05-29 19:10# Enter ? for additional hints on searching ARIN's WHOIS database.

Source:

IP Address Lookup (IPv4 & IPv6) - http://ip-lookup.net/

tech-airman

vjsousa wrote:

I will post the routing tables and running-config to this forum and any help would be appreciated.

vjsousa,

You mentioned "I have setup routing using RIP." Which version of RIP, v1 or v2?

Netstudent

Lets not hijack this guy's post over RFC 1918.
Regardless, thats not the cause of an unsuccessful ping. Unless he is using some used internet equipment with the same old startup-config.

Darthn3ss

" I don't believe that valid IP addresses, especially valid ones owned by organizations belong in a "personal lab with back to back connections."

Regardless of what you belive, i'm pretty sure that as long as its not connected to the internet, using a public IP in your lab isn't going to cause issues

my case study from the cisco networking academy had me use a public ip (200.0.0.0). I'm sure the "Latin American and Caribbean IP address Regional" didn't mind.

vjsousa

RouterA#show ip route
Gateway of last resort is not set

R 68.0.0.0/8 [120/2] via 192.168.1.2, 00:00:01, Serial1
R 172.16.0.0/16 [120/1] via 192.168.1.2, 00:00:01, Serial1
C 10.0.0.0/8 is directly connected, Ethernet0
R 72.0.0.0/8 [120/1] via 192.168.1.2, 00:00:01, Serial1
C 192.168.1.0/24 is directly connected, Serial1

RouterA#sh run
Building configuration...
Current configuration : 554 bytes
version 12.3
hostname RouterA
ip subnet-zero

interface Ethernet0
ip address 10.0.0.1 255.0.0.0

interface Serial0
no ip address
clockrate 56000

interface Serial1
ip address 192.168.1.1 255.255.255.0

router rip
network 10.0.0.0
network 192.168.1.0

RouterB#show ip route
Gateway of last resort is not set

R 68.0.0.0/8 [120/1] via 172.16.0.2, 00:00:16, Serial1
C 172.16.0.0/16 is directly connected, Serial1
R 10.0.0.0/8 [120/1] via 192.168.1.1, 00:00:04, Serial0
C 72.0.0.0/8 is directly connected, Ethernet0
C 192.168.1.0/24 is directly connected, Serial0

RouterB#sh run
Building configuration...
Current configuration : 760 bytes
version 12.3
hostname RouterB
ip subnet-zero

interface Ethernet0
ip address 72.0.0.1 255.0.0.0

interface Serial0
description Serial0 on RouterB connects to Serial1 on RouterA
ip address 192.168.1.2 255.255.255.0
clockrate 56000

interface Serial1
description Serial1 on RouterB connected to Serial1 on RouterC
ip address 172.16.0.1 255.255.0.0
clockrate 56000

router rip
network 72.0.0.0
network 172.16.0.0
network 192.168.1.0

RouterC#show ip route
Gateway of last resort is not set

C 68.0.0.0/8 is directly connected, Ethernet0
C 172.16.0.0/16 is directly connected, Serial1
R 10.0.0.0/8 [120/2] via 172.16.0.1, 00:00:21, Serial1
R 72.0.0.0/8 [120/1] via 172.16.0.1, 00:00:21, Serial1
R 192.168.1.0/24 [120/1] via 172.16.0.1, 00:00:21, Serial1

RouterC#sh run
Building configuration...
Current configuration : 543 bytes
version 12.0
hostname RouterC
ip subnet-zero

interface Ethernet0
ip address 68.0.0.1 255.0.0.0

interface Serial0
no ip address
shutdown

interface Serial1
ip address 172.16.0.2 255.255.0.0

router rip
network 68.0.0.0
network 172.16.0.0

Now I cannot ping to any of my hosts connected to my LAN from any of the routers, but I can ping the default gateways. Any help would be appreciated. See the ping tests below:
RouterA#ping 10.0.0.2 (host on E0 directly connected to RouterA)
Sending 5, 100-byte ICMP Echos to 10.0.0.2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

RouterB#ping 10.0.0.2 (host on E0 directly connected to RouterA)
Sending 5, 100-byte ICMP Echos to 10.0.0.2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

RouterB#ping 68.0.0.2 (host on E0 directly connected to RouterC )
Sending 5, 100-byte ICMP Echos to 68.0.0.2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

RouterC#ping 72.0.0.2 (host on E0 directly connected to RouterB )
Sending 5, 100-byte ICMP Echos to 72.0.0.2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

RouterC#ping 10.0.0.2 (host on E0 directly connected to RouterA)
Sending 5, 100-byte ICMP Echos to 10.0.0.2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

RouterC#traceroute 72.0.0.2
Tracing the route to 72.0.0.2

1 172.16.0.1 28 msec 28 msec 24 msec
2 * * *

RouterC#traceroute 10.0.0.2
Tracing the route to 10.0.0.2

1 172.16.0.1 24 msec 28 msec 24 msec
2 192.168.1.1 40 msec 48 msec 44 msec
3 * * *

RouterA#traceroute 72.0.0.2
Tracing the route to 72.0.0.2

1 192.168.1.2 20 msec 16 msec 20 msec
2 * *

RouterA#traceroute 68.0.0.2
Tracing the route to 68.0.0.2

1 192.168.1.2 20 msec 16 msec 20 msec
2 172.16.0.2 36 msec 32 msec 32 msec
3 *

RouterB#traceroute 10.0.0.2
Tracing the route to 10.0.0.2

1 192.168.1.1 20 msec 16 msec 20 msec
2 * * *

RouterB#traceroute 68.0.0.2
Tracing the route to 68.0.0.2

1 172.16.0.2 16 msec 16 msec 20 msec
2 * *

dtlokee

This may seem like a basic question, but do you have an active link between the host and the router interface (ie are you using crossover cables?) because if you can't ping from the router console to somthing on a directly connected interface, it's not a routing table issue. What does the output of a "show interface eth0" display for the line status?

RouterA#ping 10.0.0.2 (host on E0 directly connected to RouterA)
Sending 5, 100-byte ICMP Echos to 10.0.0.2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

Netstudent

I would also issue the no ip subnet-zero as well. Since you haven't subnetted any of your classes. You have a different network for each class, so no need to subnet or have ip subnet-zero. Also make sure you don't have a firewall that is blocking ICMP requests. Can the hosts ping the Def Gateway? Can the routers ping their directly connected ethernet network hosts?
Have you checked your ARP table? I'm not sure if ARP would come into play with the hosts being directly cabled to the interface.

vjsousa

The interfaces are up and I am using crossover cables. I will issue the IP subnet zero and try that.

vjsousa

Thanks to everyone for all your help. I have figured out the problem. It seemed to be a problem with one of the transceivers. I switched a transceiver from RouterC to RouterA and now I confirmed layer 3 connectivity throughout the network. As far as the topic of NAT goes, some of you were way off. Well, they always say, 90% of your problems are with the physical layers right.