CISCO Router Configurat

Basic Cisco Router Config with BGP Uplink

Do you have your own /24 IP subnet and want to setup a BGP router? This article will gave a basic overview of the key components required. The syntax used is for an IOS 12.2 Cisco 6500 series, but is applicable to a 7600 series, a 7200 series, or even a 1800 or 2800 series router.

Assumptions:

1. The /24 subnet we are announcing is 200.50.75.0/24.
2. The IPv4 WAN Subnet from our upstream BGP provider is 128.64.12.128/30.
3. Upstream BGP peer’s AS is 1000, and our AS is 17500

So to begin, we assume our BGP uplink is delivered to us via a basic Cat5 handoff. This handoff has a static WAN subnet of 128.64.12.128/30 – our side of the WAN is 128.64.12.130 and the provider’s side of the WAN is 128.64.12.129. That also means our default GW is 128.64.12.129.

We connect this Cat5 uplink to FastEthernet7/1 on our 6500. Now we need to go into the 6500 series router, config the WAN link, then do all the BGP configs so we can start using our /24 subnet.

OSPF Concepts

The current version of OSPF that is used for IPv4 is version 2 that was defined in Request for Comments (RFC) 2328. OSPF offers many advantages over previous routing protocols (RIP) in that it is very flexible and scalable to a number of different environments including those that are very large. OSPF is a link state routing protocol; this means that each OSPF device is tasked with maintaining a complete ‘map' of the routes available throughout the network. The OSPF metric is based on the interface bandwidth.

Summary

While the configuration of OSPF can get complex, once some basic concepts are understood a basic configuration is not all that confusing to understand or complete. The configuration of OSPF in a large scale implementation can be a bit hard to follow when quickly looking over a configuration, but if the network engineer knows the base OSPF concepts and sits down with the configuration then they should be able to figure out the intention of the OSPF design.