Quagga on Linux
From linux360
Notiuni introductive
BGP4 RFC: RFC 1772
Folosirea BGP presupune:
- detinerea unui Autonomous System Number, pe scurt AS
- detinerea unui subnet /24 (sau mai mic) de adrese IP Provider Independent, pe scurt PI
Exemple practice
Pentru a seta o sesiune BGP intre 2 neighbori (presupunand ca aveti routerele A si B si AS-urile: 65534 si 65535) faceti in felul urmator:
Router A:
RouterA# configure terminal RouterA(config)# router bgp 65534 RouterA(config-router)# network 10.2.2.0 RouterA(config-router)# neighbor 10.1.2.2 remote-as 65535 RouterA(config-router)# neighbor 10.1.2.2 description RouterB RouterA# write memory
Router B:
RouterB# configure terminal RouterB(config)# router bgp 65535 RouterB(config-router)# network 10.2.3.0 RouterB(config-router)# neighbor 10.1.2.1 remote-as 65534 RouterB(config-router)# neighbor 10.1.2.1 description RouterA RouterB# write memory
In exemplul de mai sus, fiecare router anunta cate un prefix /24 (pentru prefixe mai lungi se trece masca de retea in format CIDR).
Daca in ecuatia de mai sus se mai adauga un Router C astfel incat sa avem topologia urmatoare
RouterA <--> RouterB <--> RouterC
atunci configuratia se modifica dupa cum urmeaza:
Router B:
RouterB# configure terminal RouterB(config)# router bgp 65535 RouterB(config-router)# network 10.2.3.0 RouterB(config-router)# neighbor 10.1.2.1 remote-as 65534 RouterB(config-router)# neighbor 10.1.2.1 description RouterA RouterB(config-router)# neighbor 10.1.2.6 remote-as 65533 RouterB(config-router)# neighbor 10.1.2.6 description RouterC RouterB# write memory
Router C:
RouterC# configure terminal RouterC(config)# router bgp 65533 RouterC(config-router)# network 10.2.4.0 RouterC(config-router)# neighbor 10.1.2.5 remote-as 65535 RouterC(config-router)# neighbor 10.1.2.5 description RouterB RouterC# write memory
Daca vrem ca (e.g.) RouterB sa fie default gateway pentru celelalte doua routere, procedam dupa cum urmeaza:
RouterB# configure terminal RouterB(config)# router bgp 65535 RouterB(config-router)# network 10.2.3.0 RouterB(config-router)# neighbor 10.1.2.1 remote-as 65534 RouterB(config-router)# neighbor 10.1.2.1 default-originate RouterB(config-router)# neighbor 10.1.2.1 description RouterA RouterB(config-router)# neighbor 10.1.2.6 remote-as 65533 RouterB(config-router)# neighbor 10.1.2.6 default-originate RouterB(config-router)# neighbor 10.1.2.6 description RouterC RouterB# write memory
Folosind default-originate, pe langa prefixele exportate, se va mai exporta si 0.0.0.0/0.
Cam pana aici au fost configurarile de baza, mai jos veti gasi exemple de configurare putin mai complexe (i.e.: prefix-lists, as-prepend etc)
Pentru a nu accepta ruta default de la un anumit neighbor se face asa:
RouterC# configure terminal RouterC(config)# ip prefix-list NO-DEFAULT seq 5 deny 0.0.0.0/0 le 1 RouterC(config)# ip prefix-list NO-DEFAULT seq 10 permit any RouterC(config)# router bgp 65533 RouterC(config-router)# neighbor 10.1.2.5 remote-as 65535 RouterC(config-router)# neighbor 10.1.2.5 description RouterB RouterC(config-router)# neighbor 10.1.2.5 prefix-list NO-DEFAULT in RouterC# clear ip bgp 10.1.2.5 soft in RouterC# write memory
Daca nu vreti sa deveniti transit provider pentru altii, e bine sa stiti ce anume exportati la alti neighbori:
RouterB# configure terminal RouterB(config)# ip prefix-list our-subnets seq 10 permit 10.2.3.0/24 RouterB(config)# ip prefix-list our-subnets seq 20 deny any any RouterB(config)# router bgp 65535 RouterB(config-router)# network 10.2.3.0 RouterB(config-router)# neighbor 10.1.2.1 remote-as 65534 RouterB(config-router)# neighbor 10.1.2.1 default-originate RouterB(config-router)# neighbor 10.1.2.1 prefix-list our-subnets out RouterB(config-router)# neighbor 10.1.2.1 description RouterA RouterB(config-router)# neighbor 10.1.2.6 remote-as 65533 RouterB(config-router)# neighbor 10.1.2.6 default-originate RouterB(config-router)# neighbor 10.1.2.6 prefix-list our-subnets out RouterB(config-router)# neighbor 10.1.2.6 description RouterC routerB# clear ip bgp * soft out RouterB# write memory
