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

States

TCP

ConnectRetry timer 120 sekunder

BGP speaker försöker nå peer med TCP

TCP session established

BGP

BGP version, AS number, hold time, BGP ID
Börja skicka keepalives

Response recieved

Skicka uppdateringar
Neighbor up

router bgp [ASN]
no auto-summary

iBGP eller eBGP

neighbor [ip-address] remote-as [ASN]

Loopback

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

MD5

neighbor [ip-address] password cisco

network [ip-address] mask [subnet-mask]

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

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

show ip bgp flap-statistics

show ip bgp summary
show ip bgp neighbor
show ip bgp rib-failure

clear ip bgp *
clear ip bgp <address> soft