Cisco BGP
Border Gateway Protocol (RFC 4271) är ett path vector routing protokoll. Det kommunicerar på TCP port 179 så routing måste vara på plats, man kan nästan se det som ett L4-protokoll. BGP kan få många vägar till samma destination. Bästa vägen väljs utifrån en algoritm. http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13753-25.html
Contents
States
TCP
Idle State
ConnectRetry timer 120 sekunder
Active State
BGP speaker försöker nå peer med TCP
Connect State
TCP session established
BGP
OpenSent State
BGP version, AS number, hold time, BGP ID
Börja skicka keepalives
OpenConfirm State
Response recieved
Established State
Skicka uppdateringar
Neighbor up
Konfiguration
router bgp [ASN] no auto-summary router-id [loopback-adress]
Best practice
ip bgp community new-format
iBGP eller eBGP
neighbor 1.1.1.1 remote-as 65001 neighbor 1.1.1.1 description Other side neighbor 1.1.1.1 password 7 110B1E15
Addess family
address-family ipv4 network 10.0.0.0 redistribute isis level-2 neighbor 1.1.1.1 activate neighbor 1.1.1.1 send-community both exit-address-family
Loopback. When configuring iBGP always use loopbacks (advertised by your IGP) for peering.
neighbor [ip-address] update-source [interface]
eBGP om det ej är directly connected, t.ex. loopback
neighbor [ip-address] ebgp-multihop 2 neighbor [ip-address] next-hop-self
Nätverk som ska annonseras
network [ip-address] mask [subnet-mask]
Standard och extended
neighbor [ip-address] send-community both
Preference
bgp default local-preference 100
Synchronization is enabled by default in Cisco IOS Software Release prior to 12.2(8)T.
no synchronization
Timers
tim bg 10 30 20
För att byta från NLRI-format till AFI-format i konfigurationen
bgp upgrade-cli
Route Reflector
Routes lärda av iBGP skickas ej vidare till iBGP-grannar per default. En route reflector bryter denna regel.
Route Reflector:
address-family ipv4 neighbor [ip-address] route-reflector-client
Dampening
route-map selective_dampening permit 10 set dampening 5 1900 2000 10
5=half-life, 1900=reuse-limit, 2000=suppress-limit, 10 max-suppress-limit
router bgp [ASN] bgp dampening route-map selective_dampening
Route flap
show ip bgp flap-statistics
Show
show ip bgp summary show ip bgp neighbor show ip bgp rib-failure
Reset
clear ip bgp * clear ip bgp <address> soft
