BGP Cheat Sheet (for the BGP exercises)


ip classless
ip subnet-zero
ip bgp-community new-format
!
!--------------BGP Configuration------
router bgp 51234                        ! Initial BGP config statement
                                        ! gives your with ASN
 no synchronization                     ! Do not synchronize with the IGP
 no auto-summary                        ! no classfull boundaries
 bgp dampening                          ! dampen route flaps
 network 103.223.0.0 mask 255.255.0.0   ! network to announce into BGP
!---------------First Peer-------------
 neighbor 101.98.66.11 remote-as 51357  ! peer's address and AS number
 neighbor 101.98.66.11 description BigISP Transit (noc@upstream.net)
                                        ! name and contact info is useful
 neighbor 101.98.66.11 send-community   ! Send communities to peers
 neighbor 101.98.66.11 version 4        ! BGP version 4
 neighbor 101.98.66.11 password <BGP-password>
                                        ! password for eBGP session
 neighbor 101.98.66.11 prefix-list sanity-filter in
                                        ! filter all incoming announcements
                                        ! against this prefix-list
 neighbor 101.98.66.11 prefix-list my-routes out
                                        ! filter all outgoing announcements
                                        ! against this prefix-list

!---------------Second Peer------------
 neighbor 101.55.13.7 remote-as 53512   ! peer's address and AS number
 neighbor 101.55.13.7 description SmallISP Peering (noc@smallisp.net)
                                        ! name and contact info is useful
 neighbor 101.55.13.7 send-community    ! Send communities to peers
 neighbor 101.55.13.7 version 4         ! BGP version 4
 neighbor 101.55.13.7 password <BGP-password>
                                        ! password for eBGP session
 neighbor 101.55.13.7 prefix-list as53512-in in
                                        ! filter all incoming announcements
                                        ! against this prefix-list
 neighbor 101.55.13.7 prefix-list my-routes out
                                        ! filter all outgoing announcements
                                        ! against this prefix-list

!---------------Internal Peer----------
 neighbor 102.108.0.1 remote-as 51234   ! iBGP (remote AS is same as local AS)
 neighbor 102.108.0.1 description IBGP-peer
                                        ! useful info: neighbor description
 neighbor 102.108.0.1 version 4         ! BGP version 4
 neighbor 102.108.0.1 password <BGP-password>
                                        ! password for iBGP session
 neighbor 102.108.0.1 update-source loopback
                                        ! always use loopback for iBGP
 neighbor 102.108.0.1 send-community    ! Send communities to internal peers

!
ip prefix-list my-routes description Allow my routes and deny others
ip prefix-list my-routes seq 5 permit 128.223.0.0/16
ip prefix-list my-routes seq 100 deny 0.0.0.0/0 le 32
!
ip prefix-list as53512-in description All routes for peer AS 123
ip prefix-list as53512-in seq 5 permit 205.240.25.0/24
ip prefix-list as53512-in seq 10 permit 199.217.92.0/22
ip prefix-list as53512-in seq 15 permit 206.40.128.0/22
ip prefix-list as53512-in seq 100 deny 0.0.0.0/0 le 32
!
! prefix-list to deny some bad prefixes, permit almost everything else,
! but deny prefixes longer than /24 - see RFC3330 and Project Cymru
! (www.cymru.com/Documents) for more info
!
ip prefix-list sanity-filter description "Deny default, RFC1918, net 10"
ip prefix-list sanity-filter seq 15 deny 10.0.0.0/8 le 32
ip prefix-list sanity-filter seq 10 deny 127.0.0.0/8 le 32
ip prefix-list sanity-filter seq 20 deny 169.254.0.0/16 le 32
ip prefix-list sanity-filter seq 20 deny 172.16.0.0/12 le 32
ip prefix-list sanity-filter seq 30 deny 192.0.2.0/24 le 32
ip prefix-list sanity-filter seq 25 deny 192.168.0.0/16 le 32
ip prefix-list sanity-filter seq 50 permit 0.0.0.0/0 le 24
!