Video lab for this section @youtube:
https://www.youtube.com/watch?v=yqzEmk97ZVo&list=PL1PiPEQOeKMYqOvyKpym_dkoFY2y5BKt0
Note: This Video is in Hindi
English version below:
https://www.youtube.com/playlist?list=PL1PiPEQOeKMY3r659R5gyWt4ScTzpyg6w
BGP Basics
The main purpose of BGP is to exchange routing updates like other routing protocols, but BGP typically does not exchange individual network routes (but it technically can), it exchanges summaries of network routes. This is because the typical use of BGP is over very large networks including the Internet.
Without BGP the Internet as we know it would be quite a bit more inefficient. As it is today the Internet BGP routing tables have over 300,000 active forwarding entries and this is with summarization of over 2 billion addresses. Imagine what these tables would be like without summarization.
For those interested, some ISP’s allow the ability to telnet into their edge BGP routers to view the BGP routing tables (Check out ‘route-server.ip.att.net’).
above article is taken from : http://www.trainsignal.com/blog/bgp-border-gateway-protocol
written by sean wilkins (thanks for wonderful knowledge).
- Path vector protocol
- incremental updates
- many options for policy enforcement
- classless inter domain routing
- widely used for internet backbone
- autonomous systems
- runs top of tcp 179
A path vector protocol defines a route as a pairing between a destination and the attributes of the path to that destination.
Autonomous System (AS)
- Collection of networks with same routing policy
- single routing protocol
- usually under single ownership, trust and administrative control.
BGP BASICS:
- BGP speakers are called peers.
- Learns multiple paths via internal and external BGP speakers.
- Picks the bestpath and installs in the forwarding table.
- policies applied by influencing the bestpath selection
How BGP : neighbor relationship forms:
- 1.IDLE : verifying route to neighbor
- 2.ACTIVE: attempting connectivity to neighbor
- 3.OPEN SENT : open message to neighbour
- 4.OPEN CONFORM : neighbour replies with open message
- 4a. ACTIVE : in case of any failure
- 5.ESTABLISHED
Lab on BGP
IOU1#sh ip bgp summary
BGP router identifier 1.1.1.1, local AS number 12
BGP table version is 1, main routing table version 1
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
2.2.2.2 4 12 0 0 1 0 0 never Idle
IOU1#
*Jul 3 03:41:02.339: %BGP-5-ADJCHANGE: neighbor 2.2.2.2 Up
IOU1#sh ip bgp summary
BGP router identifier 1.1.1.1, local AS number 12
BGP table version is 1, main routing table version 1
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
2.2.2.2 4 12 4 4 1 0 0 00:00:02 0
IOU1#sh run | se bgp
router bgp 12
bgp log-neighbor-changes
neighbor 2.2.2.2 remote-as 12
neighbor 2.2.2.2 update-source Loopback1
IOU1#sh ip int brief | ex unass
Interface IP-Address OK? Method Status Protocol
Serial2/0 10.1.1.1 YES manual up up
Loopback1 1.1.1.1 YES manual up up
!!!!!!!!!!!!!!!!!!!!!111
IOU2#sh ip bgp su
IOU2#sh ip bgp summary
BGP router identifier 2.2.2.2, local AS number 12
BGP table version is 1, main routing table version 1
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
1.1.1.1 4 12 7 7 1 0 0 00:03:27 0
IOU2#sh run | se bgp
router bgp 12
bgp log-neighbor-changes
neighbor 1.1.1.1 remote-as 12
neighbor 1.1.1.1 update-source Loopback1
IOU2#sh ip int brief | ex unass
Interface IP-Address OK? Method Status Protocol
Serial2/0 10.1.1.2 YES manual up up
Loopback1 2.2.2.2 YES manual up up
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