LAN and WAN Interfaces In router




In this article we will discuss LAN and WAN Interfaces In router, will make brief discussion on LAN and WAN Interfaces. In last article we discuss about Connect to a Router – Router Ports.



LAN and WAN Interfaces

The connections on a Cisco router can be grouped into two categories: In-band router interfaces and management ports.

In-band Router Interfaces

Are the LAN (i.e. Gigabit Ethernet) and WAN (i.e., eHWICs) interfaces configured with IP addressing to carry user traffic. Ethernet interfaces are the most common LAN connections, while common WAN connections include serial and DSL interfaces.


LAN and WAN Interfaces In router
LAN and WAN Interfaces In router

Management Ports

Include the console and AUX ports which are used to configure, manage, and troubleshoot the router. Unlike LAN and WAN interfaces, management ports are not used for packet forwarding user traffic.

Similar to a Cisco switch, there are several ways to access user EXEC mode in the CLI environment on a Cisco router. These are the most common:

  • Console – This is a physical management port that provides out-of-band access to a Cisco device. Out-of-band access refers to access via a dedicated management channel that is used for device maintenance purposes only.
  • Secure Shell (SSH) – SSH is a method for remotely establishing a secure CLI connection through a virtual interface, over a network. Unlike a console connection, SSH connections require active networking services on the device including an active interface configured with an address.
  • Telnet – Telnet is an insecure method of remotely establishing a CLI session through a virtual interface, over a network. Unlike SSH, Telnet does not provide a securely encrypted connection. User authentication, passwords, and commands are sent over the network in plaintext.

Note: Some devices, such as routers, may also support a legacy auxiliary port that was used to establish a CLI session remotely using a modem. Similar to a console connection, the AUX port is out-of-band and does not require networking services to be configured or available.

Telnet and SSH require an inband network connection which means that an administrator must access the router through one of the WAN or LAN interfaces.



Serial WAN Interfaces

Added to eHWIC0 and labeled Serial 0 (i.e., S0/0/0) and Serial 1 (i.e., S0/0/1). Serial interfaces are used for connecting routers to external WAN networks. Each serial WAN interface has its own IP address and subnet mask, which identifies it as a member of a specific network.

Ethernet LAN Interfaces

Labeled GE 0/0 (i.e., G0/0) and GE 0/1 (i.e., G0/1). Ethernet interfaces are used for connecting to other Ethernet-enabled devices including switches, routers, firewalls, etc. Each LAN interface has its own IPv4 address and subnet mask and/or IPv6 address and prefix, which identifies it as a member of a specific network.

Inband interfaces receive and forward IP packets. Every configured and active interface on the router is a member or host on a different IP network. Each interface must be configured with an IPv4 address and subnet mask of a different network. The Cisco IOS does not allow two active interfaces on the same router to belong to the same network.

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