BGP
Router bợp 200 <- 200 is the AS number
Network 20.1.0.0 MASK 255.255.0.0
Neighbor 10.1.1.1 remote-as 100 <- EBGP peer
Neighbor 20.1.1.1 remote-as 200 <- IBGP peer
Aggregate-address 20.0.0.0 255.0.0.0 as-set
Neighbor 10.1.1.1 route-reflector-client
Neighbor 10.1.1.1 next-hop-self
Neighbor 10.1.1.1 ebgp-multihop
Confederations
router bgp 6001
ogo confederation identifier 666
ogo confederation peers 6002 6003
neighbor 171.69.232.55 remote-as 6002
neighbor 171.69.232.56 remote-as 6003
neighbor 160.69.69.1 remote-as 777
neighbor 10.1.1.1 update-source loopback 0
For IBGP peers only, selects loopback as source int
Show ip bgp summary Show ip bgp
Show ip bgo neighbor Debug ip bgp events Debug ip bgp updates Clear ip bgp * Show ip bgp filter-list Show ip bgp paths Communities:
Router bgp 100 neighbor 171.69.232.50 remote-as 200 neighbor 171.69.232.50 send-community neighbor 171.69.232.50 route-map set-community out route-map set-community 10 permit
match address 1 set community no-export route-map set-community 20 permit match address 2
Additional Commands
Local pref manipulation:
Access-list 1 permit 10.0.0.0 0.255.255.255
Route-map setlocalpref permit 10
Match ip address 1
Set local-preference 200
Route-map setlocalpref permit 20
Set local-preference 100
Neighbor 193.1.1.1 route-map setlocalpref in
MED:
Access-list 1 permit 10.0.0.0 0.255.255.255
Route-map setmed permit 10
Match ip address 1
Set metric 10
Route-map setmed permit 20
Set metric 50
Neighbor 193.1.1.1 route-map setmed in
Aggregate-address 160.0.0.0 255.0.0.0
Regular expressions:
matches any single character
* matches 0 or more sequence of a given pattern .* match any pattern
beginning of a string
S$ end of a string
beginning of a string, end of string or delimiter (space, comma)
ip as-path access-list 1 deny 3008
ip as-path access-list 1 permit *
neighbor 10.1.1.1 filter-list 1 out
or in attribute manipulation:
route-map setlocal permit 10 match as-path 1
set local-preference 100
Spot The Issue
must use a route-reflector or confederation
e EBGP peers must be directly connected,
otherwise must use ebgp-multi-hop
e Next hop reacheability does not change within
Otherwise, use next-hop-self at the AS border
need to redistribute BGP into the IGP
e Distribute-list in and out are applied with a
NEIGHBOR STATEMENT!! IOS will let you apply
a normal "distribute-list 1 in serial 0" but
it won't do squat!
Notes
Golden Rule: Never advertise a router that you don't know how to get to Use "show ip route” and "show ip bgp" to compare BGP advertisements and posted routes Check next-hop-reacheability localpref, weight are applied on incoming or EBGP connections MED is applied on outgoing EBGP connections
Highest local preference wins
Lowest MED wins Inter AS only
In AS only
Standard communities:
Internet: advertise to all routers No-export: do not advertise to EBGP peers No-advertise: do not advertise to any peers
local-as: Adv to IBGP or confederation peers