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Weird lab issue...

/usr/usr Member Posts: 1,768
in CCNA & CCENT
Eh, bare with me. I was trying to work this out last night at home, but couldn't figure it out. I don't have the actual output in front of me, so I'll do my best to explain the scenario.

In my lab, I have two PC's, two routers, one switch.

PC 1 is directly connected to Router 1 via a crossover cable.
Router 1 is directly connected to Router 2 via Serial 0.
PC 2 is connected to the switch, the switch to Router 2.

I have enabled RIPv2 to populate my routing table with the correct entries.

From PC 2's command line, I can ping both interfaces on Router 1 and 2, as well as PC 1.

From Router 1, I can ping the serial interface, both interfaces on Router 2, as well as PC 2.

However, from a command prompt on PC 1, I can only ping my default gateway, the ethernet interface on Router 1. I cannot ping beyond that, not the S0 interface, not PC 2, nothing.

I'm scratching my head over this one...it's like PC 1 itself is having a problem getting past it's default gateway. Why would a ping to PC 2 work from Router 1, but not PC 1, when they are directly connected and PC 1 can ping the ethernet interface?

I apologize if this was confusing without actual output. I'm at work right now...
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    EdTheLadEdTheLad Member Posts: 2,111 ■■■■□□□□□□
    So you are saying:
    1) You can ping from PC2 to PC1 but not vice versa?
    2) PC1 can ping its default gateway

    You are correct this is wierd! now i'm gonna assume what you have written above is not entrely correct and you cant ping from PC2 to PC1, then i would say:

    Are you sure that the ethernet interface on R1 is participating in rip?
    It reads like R1 has a route to all interfaces on R2, the problem is there is no route back.Issue "show ip route on R2" and verify there is a route to PC1's subnet.
    Networking, sometimes i love it, mostly i hate it.Its all about the $$$$
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    /usr/usr Member Posts: 1,768
    That's exactly what I'm saying and it is weird!

    I can ping PC1 from PC2's XP command line, but not vice versa.

    PC1 can only ping it's default gateway, the ethernet interface which it is plugged into, nothing beyond that.

    And yes, they are both participating in RIP. I've been over the show IP route output over and over again...everything is apparently correct, it's driving me nuts!
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    EdTheLadEdTheLad Member Posts: 2,111 ■■■■□□□□□□
    What happens when you switch PC1 and PC2 ? does the issue follow PC1?
    Kick off a continuous ping on PC1, "debug ip packet" on R1.
    "show interface ethernetX" on R1, send a continuous ping from PC2 and verify 100% transmission.
    Networking, sometimes i love it, mostly i hate it.Its all about the $$$$
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    /usr/usr Member Posts: 1,768
    I never tried switching them around. I didn't want to fool with switching the IP's around and what not.

    Honestly, I believe it's an issue (for whatever reason) between PC 1 and Router 1, though I haven't the slightest idea where the problem exists.

    I don't get why, when I'm sitting at the ethernet interface on Router1 via telnet, I am able to ping Router2 and PC2, but from PC1 I can only ping the ethernet interface.

    This tells me the routing table on Router1 is correct, seeing as how Router1 must use a route learned via RIP to reach PC2.

    I'm wondering if PC1 is having some weird issue with it's default gateway setting. When I specifically try to ping the gateway, I get a response. Understandable since they are in the same subnet.

    However, when I try to make PC1 use it's default gateway setting (by pinging the Serial interface on Router1), I get nothing, despite the fact that Router1 knows how to reach PC2, which is evident by the successful ping issued from Router1.

    Eh...[/i]
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    mikej412mikej412 Member Posts: 10,086 ■■■■■■■■■■
    Does PC1 have a firewall? If it does, it sounds like its set to allow only local traffic.
    :mike: Cisco Certifications -- Collect the Entire Set!
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    iwormsiworms Member Posts: 53 ■■□□□□□□□□
    /usr wrote:
    I'm wondering if PC1 is having some weird issue with it's default gateway setting.
    To find out where the ping gets "lost", I suggest using a packet sniffer (e.g. WireShark) on PC 1 and ping a remote address. In the captured ICMP, look at the layer 2 frame and see what the destination address is. If it's the Router 1 Ethernet interface's MAC address, then PC 1 is sending it to the default gateway correctly -- which means something's going on in Router 1.

    If, however, the ICMP doesn't even make it to Router 1, then it's something with your PC 1 settings.
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    /usr/usr Member Posts: 1,768
    Nah, no firewall. I checked that last night.

    I'll get back to it...

    I'm curious, but it's otherwise distracting me from studying the material I need to. I spent around 30 minutes last night.

    I will get an answer to this. icon_wink.gif
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    jason_lundejason_lunde Member Posts: 567
    What are your IP addressing schemes for lan 1, 2, and the serial connection? Make sure both are running the same version of RIP. Oh, and just check to make sure you dont have any wierd NAT settings on Router1. Baffling problem really, hope you get it worked out, and please share your findings when you do! :P
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    remyforbes777remyforbes777 Member Posts: 499
    Is this a cisco router, if so post your config.
    Remington Forbes
    www.blacksintechnology.net
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    /usr/usr Member Posts: 1,768
    I will try when I get home tonight.

    Neither router should have a weird config, considering they were wiped before I got them and I upgraded to the newest IOS.


    PC1 (LAN1) - 10.1.1.10
    Router1 Ethernet interface (Directly connected to PC1) - 10.1.1.2

    Router1 Serial0 interface (Directly connected to Router2 S0) - 10.1.2.1
    Router2 Serial0 interface (Directly connected to Router1 S0) - 10.1.2.2

    PC2 (LAN2) - 10.1.3.10
    Router2 Ethernet interface (Connected to Catalyst 2950, PC2 connected to switch) - 10.1.3.1
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    NetwurkNetwurk Member Posts: 1,155 ■■■■■□□□□□
    When a ping from XP or Vista only works in one direction from PC to PC, it's usually a Windows Firewall issue. I know you said you don't have a firewall, but you may want to double-check that the built-in Windows one is not blocking ICMP (which it does by default).

    I'd also try plugging both PCS into your switch (rather than one into the router, which is almost never done in a production network). Manually set both to be in the same network and make sure they are both in the same VLAN.
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    /usr/usr Member Posts: 1,768
    I do not use Windows Firewall, but it was what I checked last night, nonetheless.
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    remyforbes777remyforbes777 Member Posts: 499
    /usr wrote:
    I will try when I get home tonight.

    Neither router should have a weird config, considering they were wiped before I got them and I upgraded to the newest IOS.


    PC1 (LAN1) - 10.1.1.10
    Router1 Ethernet interface (Directly connected to PC1) - 10.1.1.2

    Router1 Serial0 interface (Directly connected to Router2 S0) - 10.1.2.1
    Router2 Serial0 interface (Directly connected to Router1 S0) - 10.1.2.2

    PC2 (LAN2) - 10.1.3.10
    Router2 Ethernet interface (Connected to Catalyst 2950, PC2 connected to switch) - 10.1.3.1
    Not sure what you wiping them has to do with your config not being correct but ok. I would post it anyhow if I were you.
    Remington Forbes
    www.blacksintechnology.net
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    famosbrownfamosbrown Member Posts: 637
    Didn't read all of the thread, but it looks like you are having problems pinging and you've checked Firewalls. Did you use the Setup utility or did you do everything manually? If you used the Setup Utility, did you happen to enable auto secure on one of the routers. I'm not sure if it would cause a problem since it looks like some ICMP traffic is getting through, but I'm throwing it out there anyway.
    B.S.B.A. (Management Information Systems)
    M.B.A. (Technology Management)
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    Jeffa901Jeffa901 Member Posts: 1 ■□□□□□□□□□
    No one has suggested doing a simple trace route from PC 1 so you can narrow it down to exactly where the packet is being blocked.
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    tech-airmantech-airman Member Posts: 953
    /usr wrote:
    I will try when I get home tonight.

    Neither router should have a weird config, considering they were wiped before I got them and I upgraded to the newest IOS.


    PC1 (LAN1) - 10.1.1.10
    Router1 Ethernet interface (Directly connected to PC1) - 10.1.1.2

    Router1 Serial0 interface (Directly connected to Router2 S0) - 10.1.2.1
    Router2 Serial0 interface (Directly connected to Router1 S0) - 10.1.2.2

    PC2 (LAN2) - 10.1.3.10
    Router2 Ethernet interface (Connected to Catalyst 2950, PC2 connected to switch) - 10.1.3.1

    /usr,

    What are the subnet masks for each of those IP addresses?
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    jason_lundejason_lunde Member Posts: 567
    Just looking at his subnets it looks as if his s/m is 255.255.255.0
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