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Router and Switch ping queries

Discussion in 'Routing & Switching' started by 16v6n, May 23, 2007.

  1. 16v6n

    16v6n New Member

    Hi there , I'm almost ready for my CCNA exam , and I thought I'd tr connecting up some kit I have laying around. But seem to have problems with intermittant ping replys.

    I an using 1 router 2 switches and 2 workstations... The 2 2950switches each hang off the seperarte fast ethernet port from the router going into fa0/1 on each switch. Each workstation are plugged into fa0/2 of each switch. All connected with straight cables

    I've reset both the routers and 2 swtiched back to default factory settings

    Here's the IP configurations

    (No router Serial Connections are used So I assume I need no routing Protocol?)

    Router Fa0/0
    Router Fa0/1

    Switch Vlan1
    Switch2 Vlan1


    The only commands I types into the router was the IP Add command on each interface (ip and subnet) and the no shut command.

    And the switches I have added the ip add command to the vlan and added the default gateway address of the neihbouring router interface. address.

    I can ping each switch to switch , so i know both networks are communicating , but when I ping workstation to work station or workstation any other side of the network the ping times out .. .. but intermittanlty..., theres no consistancy .

    Both the switches , routers and PC's are set at auto dectect... I've checked all the cables and even changes the routes and switches for new ones.

    And ideas why my pings might be timing out irregularly?

    Many thanks in advance.. I;ve lost some sleep with this one!
  2. NetEyeBall

    NetEyeBall Kilobyte Poster

    Do you lose any packets when you ping from switch to switch?

    When you do a ping from the switch to the connected PC do you lose packets?

    I would suggest it is a cable issue.

    If the switch can ping the router with out losing any packets then swap that cable with the one going to a PC. Then ping the switch to the router again to see if the trouble follows the cable.
    Certifications: CCNA, A+, N+, MCSE 4.0, CCA
    WIP: CCDA, CCNP, Cisco Firewall
  3. Headache

    Headache Gigabyte Poster

    One way to troubleshoot the workstations is to check the TCP/IP stack. Go into the command prompt on each PC and ping

    If the pings can back positive, then the workstations are working okay.


    Sorry, my previous entry was incorrect. Let me think about it and see if I can come with a solution.
    Certifications: CCNA
  4. Headache

    Headache Gigabyte Poster

    Okay, the problem could be down to the fact that the links between the router and two switches haven't been encapsulated and trunked. You don't really need the second switch as such. However, I've tried to come up with a topology that allows you to use both switches.

    Try this:

    1. Put the two switches in the same domain (using VTP).

    2. Create two separate vlans on each switch. Name them Vlan 10 and vlan 20 respectively. (You don't necessarily need to configure the extra vlans as such, but it's good practice for your exam).

    3. Allocate ip addresses to the both vlans on each switch. Make Vlan 10 a class B address (172.16.X.X) and vlan 20 a class C address (192.168.X.X) Apply subnetting to both sets of addresses if possible.

    4. Encapsulate and trunk the fa0/1 ports on both switches. Use 802.1q (or ISL, up to you). Connect these ports to the router via straight-through cable. i.e

    switch 1 fa0/1 => Router port fa1/0
    switch 2 fa0/1 => Router port fa2/0

    5. Go into the router and configure router-on-a-stick.

    Create 2 sub-interfaces on fa1/0


    Create 2 sub-interfaces on fa2/0


    Encapsulate all sub-interfaces (802.1q or ISL)

    Assign ip addresses to all sub interfaces:

    fa1/0.1 class B ip address (172.16.X.X)
    fa2/0.1 class B ip address (172.16.X.X)

    fa1/0.2 class C ip address (192.168.X.X)
    fa2/0.2 class C ip address (192.168.X.X)

    6. Assign ip addresses to both PCs. Use class C addresses for both PCs. (You can use class B addresses if you want, just as long as they are both in the same subnet. Bear in mind however that you have already assigned class B addresses to vlan 10 and a class C addresses to vlan 20.)

    Assign the relevant default-gateways to both PCs.

    7. Connect PC 1 to Switch 1's fa0/2 port.
    Connect PC 2 to switch 2's fa0/2 port

    8. Go into switch 1. Assign port fa0/2 to vlan20
    Go into switch 2. Assign port fa0/2 to vlan20

    9. Make sure there is no duplex and speed mismatch between the router and 2 switches.

    10. Ping all ip addresses in vlan 10 and vlan 20.

    11. Trouble shoot.

    12. Also check whether your switches support ip routing. I'm not sure if the 2950 does. (I know the 3550 does). If your switches support ip routing, then configure rip on the router and on both switches.


    Switch(config)#ip routing
    switch(config)#router rip
    switch(config)#version 2
    switch(config)#network 172.16.X.X
    switch(config)#network 192.168.X.X

    13. Let us know how you get on.
    Certifications: CCNA
  5. r.h.lee

    r.h.lee Gigabyte Poster

    1. What model is the router?

    You state "I've reset both the routers." Yet, you've already stated "I an using 1 router..."

    1. How many routers are involved?
      1. What are the model(s) of the routers?

    You stated "So I assume I need no routing Protocol..." You will need a routing protocol to route packets between two interfaces on a router, even if they're both Giga/Fast/Ethernet. Therefore, you will need to configure a routing protocol.

    1. What are the subnet masks for all of those IP addresses?

    1. For the workstations, was the IP address for the router interface or IP address for the VLAN used for the "Default Gateway?"

    1. For Switch 1, have you verified that switchport 0/1 and 0/2 are members of the same VLAN?
    2. What is the VLAN number that you're using on Switch 1?
    3. For Switch 2, have you verified that switchport 0/1 and 0/2 are members of the same VLAN?
    4. What is the VLAN number that you're using on Switch 2?

    Certifications: MCSE, MCP+I, MCP, CCNA, A+
  6. 16v6n

    16v6n New Member

    Thanks guys.. I finaly nailed it.

    I couldnt work out what the hell was going on ..

    One of the workstations (PC1) I was using has 2x network cards, 1 was used for my broadband and other was conneted to the switchport fa0/2

    What I found was odd... I could ping anything on the network but very intermittant pings to the .200 network.

    So I disabled the second network card going to the internet then I could ping right through to the .200 network reliably with zero issues. But as soon as I re-enabled the internet card it failed to get ping responses from the .200 network.

    Being windows Vista I enabled the bridging connection setting and everything popping back into life with both cards switch frimly on ... and also being able to access the internet and ping my router and switches on both sides of the network with zero packet loss.

    My PC on the .200 network also has 2x network cards installed and running windows XP.. Ive had to do nothing with this... it was was working fine from the start..

    So the problem looked like it was configuration settings in Vista (thanks Bill) so much for plug and play!

    Thanks everybody for your help. Now I can get on and try and master Access Control Lists!
  7. Headache

    Headache Gigabyte Poster

    Good. Glad to hear you managed to sort it out.
    Certifications: CCNA

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