Introduction
Telnet is a network protocol used on the Internet or LAN to provide bidirectional connection to remote hosts by using virtual terminal connection (VTY). Telnet provides access to a command-line interface on a remote machine.
Requirements
- Understanding of IPv6 Addressing Scheme
Telnet basics
Background
In this configuration example, we are trying to establish a TELNET connection with an IPV6 host (1033:ABC:33::3/64) residing at R3 from router R1. On line VTY interface and password are configured on router R3 to enable TELNET access. OSPFV3 is the routing protocol configured on the three routers (R1, R2 and R3) with all networks/prefixes participating in backbone area 0.
Note: All configurations are tested in a lab environment on Cisco 7200 series router with IOS C7200-ADVIPSERVICESK9-M), Version 15.0(1).
Topology Diagram
Configuration
Router R1Router R2Router R3Router R4
hostname R1 ipv6 unicast-routing ipv6 cef ! interface FastEthernet1/0 no ip address duplex auto speed auto ipv6 address 1011:AB01:12::1/64 ipv6 enable ipv6 ospf 10 area 0 no sh ! ip forward-protocol nd ! ipv6 router ospf 10 router-id 1.1.1.1 log-adjacency-changes end | hostname R2 ! ipv6 unicast-routing ipv6 cef ! interface FastEthernet1/0 no ip address duplex auto speed auto ipv6 address 1011:AB01:12::2/64 ipv6 enable ipv6 ospf 10 area 0 no sh ! interface FastEthernet1/1 no ip address duplex auto speed auto ipv6 address 1011:AB01:234::2/64 ipv6 enable ipv6 ospf 10 area 0 no sh ! ipv6 router ospf 10 router-id 2.2.2.2 log-adjacency-changes ! end | hostname R3 ! enable password cisco ! ipv6 unicast-routing ! ipv6 cef interface Loopback0 no ip address ipv6 address 1033:ABC:33::3/64 ipv6 enable ipv6 ospf 10 area 0 ! interface FastEthernet1/0 no ip address duplex auto speed auto ipv6 address 1011:AB01:234::3/64 ipv6 enable ipv6 ospf 10 area 0 no sh ! ipv6 router ospf 10 router-id 3.3.3.3 log-adjacency-changes ! line vty 0 4 password cisco login line vty 5 15 password cisco login ! end | hostname R4 ! ipv6 unicast-routing ipv6 cef ! interface FastEthernet1/0 no ip address duplex auto speed auto ipv6 address 1011:AB01:234::4/64 ipv6 enable ipv6 ospf 10 area 0 no sh ! ipv6 router ospf 10 router-id 4.4.4.4 log-adjacency-changes ! line vty 0 4 login ! end |
Telnet Demonstration
Note: For IPv6 Host Telnet demonstration click anywhere on the above picture.
Verify Commands
R3#sh users
Line User Host(s) Idle Location
* 0 con 0 idle 00:00:00
2 vty 0 idle 00:00:07 1011:AB01:12::1
Interface User Mode Idle Peer Address
Debugs as seen on Router R3
*Oct 9 17:49:30.083: Telnet2: 1 1 251 1
*Oct 9 17:49:30.083: TCP2: Telnet sent WILL ECHO (1)
*Oct 9 17:49:30.087: Telnet2: 2 2 251 3
*Oct 9 17:49:30.087: TCP2: Telnet sent WILL SUPPRESS-GA (3)
*Oct 9 17:49:30.087: Telnet2: 80000 80000 253 24
*Oct 9 17:49:30.087: TCP2: Telnet sent DO TTY-TYPE (24)
*Oct 9 17:49:30.087: Telnet2: 10000000 10000000 253 31
*Oct 9 17:49:30.091: TCP2: Telnet sent DO WINDOW-SIZE (31)
*Oct 9 17:49:30.207: TCP2: Telnet received DO SUPPRESS-GA (3)
*Oct 9 17:49:30.211: TCP2: Telnet received WILL WINDOW-SIZE (31)
*Oct 9 17:49:30.211: TCP2: Telnet received WILL LOCAL-FLOW (33)
*Oct 9 17:49:30.211: TCP2: Telnet sent DO LOCAL-FLOW (33)
R3#
*Oct 9 17:49:30.215: Telnet2: Sent SB 33 0
*Oct 9 17:49:30.363: TCP2: Telnet received DO ECHO (1)
*Oct 9 17:49:30.395: TCP2: Telnet received WONT TTY-TYPE (24)
*Oct 9 17:49:30.395: TCP2: Telnet sent DONT TTY-TYPE (24)
*Oct 9 17:49:30.399: Telnet2: recv SB NAWS 80 24
