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Can't ping or telnet

By Mick@work ·
Folks,

I have a lan with a 23 bit mask and 5 cisco 2950 switches and at the core a 4006 switch which connects to a 7000 series router as the gateway.

My problem:

From a node on the lan i can ping the gateway but no-one of the switches. I can ping out of the lan to other lans successfully

From the console of any of the switches i can ping the other switches and see them all using Cisco CDP - I can also telnet to other switches.

All switches have the gateway set as the ip default gateway.

Any ideas why i can't ping from any of the lan nodes or telnet to my switches?

Any suggestions gratefully received

thanks

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Can't ping or telnet

by stolson In reply to Can't ping or telnet

Typically, when you can't ping locally, but can ping the gateway and other LANs, it's a subnet mask problem on the node. If you post a node's information (IP, sub mask, def gateway)and a switches, I can tell you more.

Steve Olson

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Can't ping or telnet

by Mick@work In reply to Can't ping or telnet

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Can't ping or telnet

by Magickl In reply to Can't ping or telnet

I would start at the Gateway. My first suspicion would lay in the 7000 acting as the Gateway and the routing information becoming lost, the packet may get lost on the return.
I begin by turning on the ICMP Debugging at the 7000 and monitor the initial responses. While in "ENABLE" mode at the 7000 console, or if you telnet to the 7000 remotely be sure and type "TERM MON" (this will out put the results to the accessing terminal. The type "DEBUG IP ICMP EVENT". Initially just start with a machine you cannot get to in the method you refer to in your message.
type "PING <ip address of machine>"
observe your results and verify that the ping message leaving the 7000 and going out the interface that is connected to the Cat 4006.
Next do a "SHOW IP ROUTE <ip address of the machine you pinged>"
If the ping is going out the proper interface, try and "TRACE IP <IP of the machine>". Observe where the Traceroute begins to hang.
If the initial Ping was unsuccessful, I would next do an extended ping using the IP address of the Particular interface facing the 4006 as the source address when prompted. If that ping works, the router's route table needs to be examined. If you are using OSPF, be sure the network is in your OSPF table on the router. You will immediately know it is not if the first "SHOW IP ROUTE <IP address>" resulted with a "not in table" message.
I am assuming too much... It will still be the 7000 "gateway"'s responsibility in the beginning. If you have VLANS assigned on the remote 2950 switches, and/or your "Bridge Group" command is incorrect, the problem becomes a little more complex.
After the you are done with the DEBUG of the IP ICMP, be sure and turn it off with "UNDEBUG ALL" or "UNDEBUG IP ICMP".
More information would be required on your part, for example: Are the addresses of the remote LANS PUBLIC or PRIVATE?
I hope this has been able to get you jump started at least.

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Can't ping or telnet

by Mick@work In reply to Can't ping or telnet

It turned out to be a vlan problem. 6 switches were on vlan 1 while the gateway was on vlan 3.

Problem resolved

Thanks

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Can't ping or telnet

by Zen37 In reply to Can't ping or telnet

It sounds to me like you may have a VLan issue.
Has ALL your ports been assigned a VLan? are they all the same ( is the one you cannot ping from on a different VLan than the others )?

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Can't ping or telnet

by Mick@work In reply to Can't ping or telnet

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Can't ping or telnet

by Mick@work In reply to Can't ping or telnet

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