Console and VTY
The Cisco router can be configured from many locations.
1. Console port: During the initial installation, you configure the router from a console terminal connected to the "Console port" of the router.
2. Virtual Terminals (vty): A virtual terminal (vty) is typically accessed through Telnet. A router can be accessed through vty after the initial installation in the network. There are five virtual terminals, namely, vty0,vty1,vty2,vty3,vty4.
3. Auxiliary Port: you can configure a router through auxiliary port. Typically, a modem is used to configure the modem through aux port.
4. TFTP Server: Configuration information can be downloaded from a TFTP server over the network.
5. NMS (Network Management Station): You can also manage router configuration through NMS such as CiscoWorks or HP OpenView.
Internet Protocol (IP) networks use managing devices such as Simple Network Management Protocol (SNMP) to monitor network attached devices. In a computer network, a group of devices are attached, and they are managed and monitored by a manager. An agent, which is a software module in a managed device, reports information through the SNMP to the manager which has a Network Management System (NMS) that executes the applications that monitor and control managed devices.
| Security Model | Security Level | Authentication | Encryption Type |
|---|---|---|---|
| SNMPv1 | noAuthNoPriv | Community string | None |
| SNMPv2c | noAuthNoPriv | Community string | None |
| SNMPv3 | noAuthNoPriv | User name | None |
| AuthNoPriv | MD5 or SHA | None | |
| authPriv | MD5 or SHA | CBC-DES (DES-56) |
The DHCP Discover message is sent as a broadcast on the network.DHCP messages are as below:
DHCP DISCOVER: broadcast the client computer sends out a broadcast on the LAN because it does not know where the DHCP server is.
DHCP OFFER: unicast. The broadcast is received by the DHCP server and it responds with a DHCP offer which contains an IP address, Subnet Mask and Default Gateway and any other optional information (configured on the DHCP server).
DHCP REQUEST:broadcast. The client computer gets the IP info, with the corresponding Subnetmask and Default Gateway, from the DHCP server. When the client computer decides it is going to use the IP address, it lets the DHCP server know that it will accept the IP address that was send by the DHCP server. So it send out a request, asking the DHCP server if it can use the information/IP provided by the DHCP server. The Client does this by the means of unicast. The client computer now knows what IP address the DCHP server uses and send this message as a unicast.
DHCP ACK: broadcast or unicast.The DHCP Request comes in at the DHCP server and the DHCP server will then send a DHCP ACK packet to the client. This packet includes the lease duration and any other configuration information that the client might have requested.