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switch killing connection to router

John Huthmaker
Enthusiast
Enthusiast

I'm working on my cisco lab.  Every device is plugged in to my switch (computer, router, firewall).  Whenever I telnet from my computer direct to my router, it works for a second and then disconnects.  I cant then reconnect.  If I telnet to my switch first, and then telnet from my switch to my router, it works fine. I tried connecting my router to different ports on the switch.  Why does it do this?

8 REPLIES 8

John Huthmaker
Enthusiast
Enthusiast

Does anybody know what is causing the above?

fb_webuser
Frequent Contributor
Frequent Contributor

Does everything have a unique IP address?

do show ip arp on the routers and arp -a on your PC perhaps the arp tables are getting messed up.

If you connect by telnet while monitoring the serial port do you get any messages ?

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Posted by WebUser Stuart Gall

Everything does have a unique IP Address.  I will run the above commands tonight when I have a chance.

I just want to be clear on the last sentence.  You want me to console in to the router, and then also connect over telnet and see if the console gives me a message.  Is that right?

jas2061461
Beginner
Beginner

Can you ping the router interface from your PC. Sometimes being connect to a WAP while plugged into a different network, such as your switched network, can cause issues; disable secondary network connections.  Sometimes Windows firewall can cause issues; disable that.  Post any configs you have available.

Here is a breakdown of my network.

Fortigate Fortinet 200a Firewall 10.0.0.1 (Running DHCP Services)

Cisco 3548XM Switch 10.0.0.2 (VLAN1)

Cisco 2611 Router 10.0.0.3

My computer 10.0.0.100 (recieved from DHCP - Directly plugged in to switch)

If I telnet to 10.0.0.3 it makes a connection and prompts me to login.  Before I can complete the login it disconnects me, and I cannot reconnect.  I can ping 10.0.0.3 just fine.  I can then telnet to 10.0.0.2 and login, and then telnet from there to 10.0.0.3 and it works fine.