no ping - 2 routers connected via cross over cable

[witek77]

Hello Everyone.

I have bought 2 cisco 2600 routers. Got them connected with cross over cable, configured the interfaces on both sides and get no ping getting from one side to the other? Can anyone tell me why,please? IP adresses for both connected interfaces are 192.168.2.1 and 192.168.2.2 with 255.255.255.0 mask. I've tried full-duplex and half-duplex. still get no signal either on putty connected to console port on one of them or from laptop connected to the other Ethernet port?

[Richard Burts]

Witek

This is an interesting situation. In general if ping works in one direction we would expect that it would also work in the other direction.

To help us understand the issue can you tell us which device/what IP address is the source of the ping and what device/what IP address is the destination of the ping?

Can you try a traceroute (or tracert depending on OS) and post the results. Perhaps do both ping and traceroute in the direction that does work and then ping and traceroute in the direction that does not work?

[witek77]

Hello again,

Here is ping from 1700 to laptop

adam2#ping 192.168.1.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms

Funny thing is yesterday I also changed the default gateway on Ethernet Adapter Local Area Connection to 192.168.1.1matching it with IP address of 2600 router's interface it is connected to. But then at the end I changed it hoping that ping will get through from laptop through 2600 router to 1700 router. And I could do ping from 1700 to laptop without it.

So this has to be on as well which I've thought is strange because Wireless LAN adapter Wireless Network Connection has got exactly the same Default Gateway IP Address?Anyway I've pasted it underneath

Wireless LAN adapter Wireless Network Connection:

   Connection-specific DNS Suffix  . : home

   IPv6 Address. . . . . . . . . . . : 2a01:116f:555:8000:756e:7b8d:3ee0:b8d3

   Temporary IPv6 Address. . . . . . : 2a01:116f:555:8000:48ed:a893:8829:5398

   Link-local IPv6 Address . . . . . : fe80::756e:7b8d:3ee0:b8d3%12

   IPv4 Address. . . . . . . . . . . : 192.168.1.14

   Subnet Mask . . . . . . . . . . . : 255.255.255.0

   Default Gateway . . . . . . . . . : fe80::dad7:75ff:fe22:4da%12

                                       192.168.1.1

Ethernet adapter Local Area Connection:

   Connection-specific DNS Suffix  . :

   Link-local IPv6 Address . . . . . : fe80::a9:7ca5:99bd:730b%11

   IPv4 Address. . . . . . . . . . . : 192.168.1.100

   Subnet Mask . . . . . . . . . . . : 255.255.255.0

   Default Gateway . . . . . . . . . : 192.168.1.1

So maybe it's some kind of a conflict?Am I understanding that correctly that my internet wireless router has given my laptop wireless adapther 192.168.1.14 IP address but it's own inbound interface IP address is 192.168.1.1?

Anyway I send you all the details first.Ping gets through from 1700 router to laptop and that is the traceroute for it:

adam2#traceroute 192.168.1.100

Type escape sequence to abort.
Tracing the route to 192.168.1.100

1 192.168.2.2 0 msec 0 msec 4 msec
2 * * *
3 * * *
4 * * *
5 * * *
6 * * *
7 * * *
8 * * *
9 * * *
10 * * *and like this till no. 30

it shows only first hop and then the stars? but ping still gets through?

I will try the other way round

C:\Users\witek>ping 192.168.2.1

Pinging 192.168.2.1 with 32 bytes of data:

Request timed out.

Request timed out.

Request timed out.

Request timed out.

Ping statistics for 192.168.2.1:

    Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

Ping still doesn't get trough. Here is the tracert command effect:

C:\Users\witek>tracert 192.168.2.1

Tracing route to 192.168.2.1 over a maximum of 30 hops

  1     2 ms     2 ms     1 ms  funbox.home [192.168.1.1]

  2    34 ms    34 ms    34 ms  192.0.0.1

  3     *        *        *     Request timed out.

  4     *        *        *     Request timed out.

  5     *        *        *     Request timed out.

  6     *        *        *     Request timed out.

  7     *        *        *     Request timed out.

  8     *        *        *     Request timed out.

  9     *        *        *     Request timed out.

 10     *        *        *     Request timed out.

And like this till no. 30

Trace complete.

[Richard Burts · Accepted solution]

Witek

Thanks for the additional information. I am slightly surprised to see that the computer has both an active wireless connection and an active Ethernet connection. 

Pretty clearly when you ping from 1700 to computer it is using the Ethernet connection on the computer - and it works. I wonder when you attempt to ping from the computer if perhaps it is using the wireless connection? Would you turn off the wireless on the computer and try the ping when the computer has only a single active interface - Ethernet?

[witek77]

Hello,

Tahnk you very much, it worked and now I can send ping both ways. Before I turned the wireless off I also send an extended ping from 192.168.1.1 interface so the interface which connects 2600 router with laptop to the 1700 router and that ping also got through which made my hopes a bit higher. Yes, but when I finally turned it off i got the signal trough. One last thing -  tracert 192.168.2.1 command on the laptop shows those two hops a ping has to jump to be able to get to the 1700 router but when I write traceroute 192.168.1.100 command on the 1700 router to show me route it has to mak to get to the laptop I get the result like this:

adam2#traceroute 192.168.1.100

Type escape sequence to abort.

Tracing the route to 192.168.1.100

  1 192.168.2.2 0 msec 0 msec 4 msec

  2  *  *  *

  3  *  *  *

and so on 30 times

Can you tell me why it does that?

[Richard Burts]

I believe that it is doing this because of the firewall on the computer. You made a firewall rule to accept ping. But traceroute from the 1700 does not use ping. It uses a UDP packet. I believe that the computer firewall is denying the UDP packet and so traceroute does not work.

[witek77]

Hello again,

Thank you for pointing out the reason behind the traceroute command not working properly. Same as I did with ICMP Echo Request I did an additional Inbound ,and just in case it has any influence outbound, rule in windows firewall allowing UDP packets to get through but it doesn't change anything. Is there anything else I should do or shall I only allow certain UDP ports to get open?

[Richard Burts]

tracert from Windows machines uses ICMP probe packets. traceroute from Cisco (and many *nix systems) use UDP probe packets. And they may use a variety of UDP port numbers. So if you want these traceroute packets to work you probably should just set a firewall rule to accept all UDP packets.

[witek77]

Hello,

The thing is that I already did and unfortunatelly it doesn't work. But I will try to turn the firewall off for a moment and see if that works. Thanks