Cisco 2511 Part 1

05 Aug 2019

I got the lab network working, and I got recommended another book to review before the test from the coworker that I bought the hardware from. Cisco CCNA in 60 Days by Paul Browning. It’s been a great structured review so far with the review text, exercises, practice labs, and practice exams. I’m currently through Day 5.

Another cool piece of tech that my coworker gave me was an old Cisco 2511 Access Server / Router. There is this cable referred as an “Octal to RJ45.” It is cabled in such a way that allows you to plug into the ASYNC port on the Cisco 2511 then connect up to 8 devices via their console port. This will be great because when I practice remotely, I can make mistakes without being locked out of my equipment at home. I can also regularly clear out the config. I’ve had it for a couple weeks but didn’t have time to play with it. (The 2511 is at the bottom of the stack in the picture below)

Today I finally went to go use it, and the config that was saved on it when he gave to me was lost. So, lesson learned to save the config even in a lab environment. Especially on something you don’t know how to operate yet. I was able to google search a bit to find the answer and I got it working!

Cisco 2511 Working Config File

R_2511#show run
Building configuration...

Current configuration : 1099 bytes
!
version 12.1
no service single-slot-reload-enable
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname R_2511
!
!
username myusername privilege 15 password 0 mypassword
!
!
!
!
ip subnet-zero
ip domain-list cisco.com
no ip domain-lookup
ip host SW2 2008 172.21.1.1
ip host SW1 2006 172.21.1.1
ip host R3 2007 172.21.1.1
ip host R2 2002 172.21.1.1
ip host R1 2001 172.21.1.1
!
!
!
!
interface Loopback0
 ip address 172.21.1.1 255.255.255.255
!
interface Ethernet0
 ip address 172.16.25.11 255.255.255.192
 no ip mroute-cache
!
interface Serial0
 no ip address
 no ip mroute-cache
 shutdown
!
interface Serial1
 no ip address
 shutdown
!
ip default-gateway 172.16.25.1
ip classless
ip route 0.0.0.0 0.0.0.0 172.16.25.1
no ip http server
!
!
line con 0
 transport preferred telnet
 transport output pad v120 telnet rlogin udptn
line 1 16
 session-timeout 60
 exec-timeout 0 0
 no exec
 transport input telnet
line aux 0
 transport preferred telnet
 transport input all
 speed 38400
 flowcontrol hardware
line vty 0 4
 exec-timeout 0 0
 login local
!
end

R_2511#

I didn’t have any experience before doing ‘reverse telnet’. I got stuck inside my session for a bit trying to figure out why the key combination CTRL + SHIFT + 6 + X wasn’t working. Turns out I was just doing it wrong. A more accurate representation would be hold down (CTRL + SHIFT + 6) Let go of those 3 keys and immediately press x. Once you get back into your previous router, you’ll need to disconnect the session, so it doesn’t stay open.

The next problem I encountered was that I couldn’t login through a telnet connection. (This equipment is pre SSH era) It was stating no password set. There isn’t any config for a password on Ethernet0, so since it is a telnet/ssh connection it has to be a VTY line configuration issue.

I have ‘login local’ set on ‘vty 0 4’ so it should use my lab login that I configured.

show run
username myusername password mypassword

I can see that I have a username and password set. I then thought, well maybe there isn’t high enough permissions on the account. Because everything else seems correct, so let’s give that a try.

username myusername privilege 15 password mypassword

telnet 172.16.25.11

User Access Verification
Username: myusername Password: 
R_2511#

Cool it’s working now!

The fun never ends though. I’m at work now and I can’t login to Router 3, Switch 1, or Switch 2. I can only login to Router 1 & 2. I was getting this error.

Trying SW2 (172.21.1.1, 2005)… % Connection refused by remote host

Meanwhile a successful connection should look like this.

R_2511#r1 Trying R1 (172.21.1.1, 2001)… Open

After I got home. It turned out to be some bad cables from the old equipment. Lucky for me I had 5/8 good cables. Just barely enough to hook it all 5 pieces of equipment.
Cable 1 goes to R1
Cable 2 goes to R2
Cable 7 goes to R3
Cable 6 goes to SW1
Cable 8 goes to SW2

I removed the old test config

no ip host C9 2009 172.21.1.1
no ip host C8 2008 172.21.1.1
no ip host C7 2007 172.21.1.1
no ip host C6 2006 172.21.1.1
no ip host SW2 2005 172.21.1.1
no ip host SW1 2004 172.21.1.1
no ip host R3 2003 172.21.1.1

Put the new config

ip host R3 2007 172.21.1.1
ip host SW1 2006 172.21.1.1
ip host SW2 2008 172.21.1.1

Learning Sources:
https://www.cisco.com/c/en/us/support/docs/dial-access/asynchronous-connections/5466-comm-server.pdf
https://community.cisco.com/t5/switching/kill-vty-session-on-catalyst-2950/td-p/2204810
https://community.cisco.com/t5/other-network-architecture/ctrl-shift-6-x-combination-for-telnet/td-p/284885