Bgp maintains a separate routing table based on shortest as path and various other attributes, as opposed to igp metrics like distance or cost. Good source to practice bgp attributes weight, local pref. The bgp session established between router r1 and router r2 is done using ipv6. Bgp border gateway protocol is an exterior gateway protocol also known as path vector routing protocol is designed to exchange the routing information between the autonomous systems as. Name bgp path attributes to control incoming and outgoing traffic. We support bgp versions 2, 3, and 4, as defined in rfcs 1163, 1267, and 1771, respectively. Attributes in action router1sh ip bgp bgp table version is 28, local router id is 100. Mar 23, 2012 if bgp alwayscomparemed was also enabled then comparing entry1 the winner from group 1 and entry 2 the winner from group 2, entry 1 will be the winner because of lower med. What is the difference between when a route is injected in bgp via redistribute command or a network command. In addition, if bgp alwayscomparemed is enabled, bgp med decisions are always.
Each router team should check peerings to see the effect of this step. The bgp next hop attribute is the next hop ip address to use in order to reach a certain destination. Device interface iipv4 address subnet default gateway r1 campus network r1. However, configure router 1 and router 12 as route reflector servers in their respective ass. Description of bgp route reflection a bgp speaker is a bgp enabled router.
Configure bgp path attribute manipulation to effect routing. Configure the ip addresses on the routers using the following 192. In the example in this section, rtc advertises 170. Because the aspath attribute is set after the prefix lists, aspath filters. If you need some more help understanding bgp, take a look at my how to master ccnp route book. This article describes different scenarios of border gateway protocol bgp route reflection and usage of multiple cluster ids. Bgp and bgp path attributes typically bgp is an egp exterior gateway protocol category protocol that widely used to connect different as routing domain. Bgp border gateway protocol uses an attribute list for path selection. Device interface iipv4 address subnet default gateway r1 campus network r1eth0 192. Nurul maintains the apnic training lab and is involved in delivering technical training for the apnic community.
Border gateway protocol bgp 1 15 outline 1 introduction 2 bgp operation border. This video explains you how to solve the bgp attribute as path lab found on gns3vault. Part 2 configuring bgp in this lab part you first verify the autonomous system from networking 101 at victoria university. Igp has a higher preference than egp which has a higher preference than incomplete. Configuring mp bgp page 6 r1 r2 ipv6 lan 1 ipv4 bgp session advertise ipv6 lan 1 192. Bgp is simple straightforward protocol but it become complex when networks grows and need expertise in bgp implementation while you working in enterprise network environment bgp runs over tcp protocol on port 179 and for this pointto. Module 7 bgp route filtering and advanced features. Use the show ip bgp command to show the bgp table ensure that the external prefixes learned by bgp. Use the show ip bgp command to show the bgp table ensure that the external prefixes learned by bgp now have a local nexthop address. In this lesson, you learn the bgp attributes and how bgp selects the best path. To verify the bgp operation on ita, issue the show ip bgp command. Bgp has multiple path attributes to influencing traffic flow. Configuring 4byte as numbers and bgp extended community attributes 331. Weve included weight in the list, now weight is not strictly a bgp attribute, in that its not passed within the bgp update information, its only local to the.
The bgp attribute aspath is the fourth bgp attribute. Ensure that all bgp updates between peers are sourced from each routers loopback interface. Addis ababa university addis ababa institute of technology school of electrical and computer engineering telecommunication networks lab vi. At each router, the bgp decision process ranks routes based on the attributes for. Jan 21, 2016 nice way simulating the internet in your lab environment, kevin. Here we go again, in this post about bgp we will explore how to inject full internet routing table in our lab and how to test some operations of bgp prefix origin validation. Bgp peerings to demonstrate neighbour filtering and more advanced ios features.
To verify the configuration, check the ita routing table with the show ip route command. And, to influence outgoing traffic, weight and local preference are the best choices. In this lab, bgp will be configured as the exterior gateway protocol egp and open shortest path first. In this lab, you will configure mp bgp, bgp for ipv4 and ipv6 using address families. Bgp attribute used to group destinations represented as an integer each destination could be member of multiple communities community attribute carried across ass useful in applying policies. Sep 30, 2020 a bgp router will prefer routes that it installed into bgp itself, over a route that another router installed in bgp. Understanding a 4byte capable router as path through a. I will show you how to configure bgp routing protocols on cisco router using three router. Border gateway protocol lab series principal investigator. It is an exterior gateway protocol egp that is used to. Configuring ibgp and ebgp sessions, local preference.
This is a bgp configuration example lab showing bgp configuration using cisco packet tracer. Lab exercise on basic router and ospf dynamic routing. Border gateway protocol bgp is considered a path vector routing protocol. The communities bgp path attribute is an optional transitive attribute made up of 32 bits. There is a variable sequence of bgp attributes in every update message except for those that carries only withdrawn routes. Rightclick on any router click select similar nodes make sure that all routers are selected rightclick on any router edit attributes check the apply changes to selected objects check box. Then bgp best path selection continues with local preference and so on. Basic bgp lab configuring basic bgp lab basic objectives. For ebgp, the next hop is always the ip address of the neighbor that the neighbor command specifies.
Basic bgp configuration yonas yehualaeshetemail protected june 6, 2019 learning objectives upon completion of this lab, you will be able to. This lab introduces and configures the border gateway protocol bgp next hop attribute and explains how this attribute is transmitted in external bgp ebgp and internal bgp ibgp. This course has made it very easy for students to understand the bgp concepts. See pdf for screenshot, see zip file for lab edited. Advertising an ipv6 lan address through a bgp ipv4 session. Prior knowledge of bgp concepts especially clusters and route reflection is assumed. Added interface labels and pulled routers away from each. May 26, 2011 having bgp between isp, or between as that creates internet makes perfectly sense what i dont get is why i should use bgp in my company lets admit that for some reasons i must find the best path to reach a destination, if for example i have a branch somewhere in the world i cannot understand why me, an isp client, should use bgp to push routes into bgp ip address are. Bgp attributes path selection algorithm bgp attributes. There are a couple of wellknown communities defined in bgp such as those defined in rfc 1997 as follows. It has many labs which will eventually make you comfortable working with bgp. This origin attribute is used in bgp path selection as follows.
Configuring bgp route selection using bgp attributes discovery lab 31. Cisco recommends enabling bgp deterministicmed in all new network deployments. As a result of this experiment, a small, but significant percentage of global internet traffic was disrupted for a period of about 30 minutes. In the most common practice we do manipulate incoming traffic using aspath prepending and med multiexit discriminator. Bgp path attributes attributes describe the path to a networksnlri used to enforce routing policies for path control. Configure and cable the serialethernet interfaces as indicated in the above diagram. Weight attribute is a cisco proprietary bgp path attribute that is the first step in the bgp best path selection algorithm. The bgp nexthop attribute is the next hop ip address that is going to be used to reach a certain destination. For ebgp, the next hop is always the ip address of the neighbor specified in the neighbor command.
Bgp is a standardized exterior gateway protocol egp. In this lab, we will be looking at more advanced capabilities of bgp. Bgp attributes are pieces of information that a bgp router attaches to describe different prefixes included in its bgp update messages. Form ibgp and ebgp neighbor relationships where appropriate. This lab is an exercise in developing, deploying, and verifying various path manipulation tools for bgp, and does not reflect networking best practices. Each attribute is a tlv that consists of attribute type, attribute length and attribute. Ripe ncc and duke university bgp experiment on 27 august 2010, the ripe nccs routing information service ris was involved in an experiment using optional attributes in the border gateway protocol bgp. Device interface iipv4 address subnet default gateway router r1 r1eth0 192. The lab exercises use cisco ios configuration syntax. Expand the bgp parameters hierarchy and set the following. The internet is a successful experiment that escaped from the lab.
It is used to group routes that share a common property. Feb 19, 2018 in this article i am going to show you how to configure bgp step by step. Bgp attributes path selection algorithm influence inout. How bgp routers use the multiexit discriminator for best. In bgp, each route consists of a network number, a list of autonomous systems that information has passed through called the autonomous system path, and a list of other path attributes. Bgp runs over tcp protocol on port 179 to pass the bgp messages among routers and to allow the neighboring routers to reside on the same subnet. Local preference bgp default localpreference 100 route map neighbor 172. Participants are advised to bring their own laptop computers with highspeed wifi 802.
Its an important topic to understand if you work at an isp or at a large company that is connected to two or more isps. Configuring advanced bgp lab continued bgp objectives. Configure bgp to exchange routing information with two isps. Bgp practicals zerotohero live instructorled online. Furthermore, the lab presents full mesh topology used in ibgp. Bgp p art 1 type about bgp ebgp ad ibgp ad path vector 20 200 standard protocols transport authentication rfc 4271 ip tcp179 md5 path selection attribute weight administrative preference description 1 preference highest local preference communicated between peers within an as 2 highest 3 selforiginated prefer paths originated locally true. Both routes have the same value for all attributes, the only difference is the way they have been learnt. Lab setup for bgp the above diagram will be used for studying all bgp concepts in the ccnp route 642902 curriculum, plus ccie topics like route reflectors and confederations. Virtualization and distribution of the bgp control plane.
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