1-1-1. Cisco Single BGP with Default Route

   April 9, 2008
BGP sample configuration 1-1-1

 

  • ISP: 1
  • WAN link: 1
  • CPE: 1
  • PE: 1
  • Device: Cisco router with LAN/WAN ports.
  • WAN / Serial IP: 12.1.3.0/30 (mask 255.255.255.252)
  • LAN / Ethernet IP: 10.1.0.0/24 (mask 255.255.255.0)
  • Receiving Route: Default route + full route from ISP
  • Memory: Full route(recommend 512M), partial route
    (recommend 128-256M)
  • LAN: ISP (AS20) and Customer (AS10)
  • Comments: If you have only single link with ISP, you don’t really need BGP protocol at all. Better to use just default route to save even bandwidth. Consult with professionals if really need it. This article is shown for educational purpose.
 BGP sample configuration 1-1-1

 

[CPE/Customer Cisco Router]

Current configuration

hostname CPE
!
interface Ethernet0
description to Internal network
ip address 10.1.0.1 255.255.255.0
no ip directed-broadcast
no ip mroute-cache
!
interface Serial0
description to ISP
ip address 12.1.3.1 255.255.255.252
no ip directed-broadcast
no ip mroute-cache
no fair-queue
!
router bgp 10
no auto-summary
network 10.1.0.0 mask 255.255.255.0
neighbor 12.1.3.2 remote-as 20 <—— ISP’s ASN
neighbor 12.1.3.2 version 4
neighbor 12.1.3.2 prefix-list 1 out
!
ip classless
!
ip prefix-list 1 description announcing routes to ISP
ip prefix-list 1 seq 5 permit 10.1.0.0/24 le 32
!
line con 0
line aux 0
line vty 0 4
login
!
end
[PE / ISP Cisco Router]
Current configuration:
!
hostname PE
!
interface Serial0
description to ISP
ip address 12.1.3.2 255.255.255.252
no ip directed-broadcast
no ip mroute-cache
no fair-queue
!
router bgp 20
neighbor 12.1.3.1 remote-as 10 <—- Other side’s ASN
neighbor 12.1.3.1 version 4
neighbor 12.1.3.1 default-originate <—- Sending default route to customer through BGP.
neighbor 12.1.3.1 prefix-list 2 in
!
ip classless
!
ip prefix-list 2 description from customer or peer
ip prefix-list 2 seq 5 permit 10.1.0.0/24 le 32 <—- Accepting smaller block than /24
!
line con 0
line aux 0
line vty 0 4
login
!
end
[Verifing output]
CPE# show ip bgp neighbors 12.1.3.2 ad
BGP table version is 8, local router ID is x.x.x.x
Status codes: s suppressed, d damped, h history, * valid, > best, i – internal
Origin codes: i – IGP, e – EGP, ? – incompleteNetwork Next Hop Metric LocPrf Weight Path
*> 10.1.0.0/24 0.0.0.0 0 32768 ?
CPE#
CPE#show ip bgp nei 12.1.3.2 ro
BGP table version is 8, local router ID is x.x.x.x
Status codes: s suppressed, d damped, h history, * valid, > best, i – internal
Origin codes: i – IGP, e – EGP, ? – incomplete
Network Next Hop Metric LocPrf Weight Path
*> 0.0.0.0/24 12.1.3.2 0 0 20 ?
Total number of prefixes 1
PE#show ip bgp nei 12.1.3.1 ro
BGP table version is 8, local router ID is x.x.x.x
Status codes: s suppressed, d damped, h history, * valid, > best, i – internal
Origin codes: i – IGP, e – EGP, ? – incomplete
Network Next Hop Metric LocPrf Weight Path
*> 10.10.10.0/24 12.1.3.1 0 0 10 ?
Total number of prefixes 1

If you have any questions, feel free to send email us at [email protected]. If you are looking for professional grade service, you might want to try our “BGP experts service“. What is “BGP Experts service“? Click “BGP Experts” from the top menu option. You will find out what the “BGP Experts” and what we are doing here for.

Author: admin