TASK
as-overrideってBGPネイバ以外(直前のAS番号以外)も書き換えるんだっけ？という疑問から確認してみた。
DIAGRAM
CONFIG
hostname R1 ! interface Loopback0 ip address 10.0.0.1 255.255.255.255 ip ospf 1 area 0 ! interface FastEthernet0/0 ip address 10.1.2.1 255.255.255.0 ip ospf 1 area 0 no shutdown ! interface FastEthernet0/1 ip address 10.1.3.1 255.255.255.0 ip ospf 1 area 0 no shutdown ! router ospf 1 mpls ldp autoconfig ! end
hostname R2 ! vrf definition VPN-USER-A rd 65000:65099 route-target export 65000:65099 route-target import 65000:65099 ! address-family ipv4 exit-address-family ! interface Loopback0 ip address 10.0.0.2 255.255.255.255 ip ospf 1 area 0 ! interface FastEthernet0/0 ip address 10.1.2.2 255.255.255.0 ip ospf 1 area 0 no shutdown ! interface FastEthernet0/1 vrf forwarding VPN-USER-A ip address 10.2.4.2 255.255.255.0 no shutdown ! router ospf 1 mpls ldp autoconfig ! router bgp 65000 no bgp default ipv4-unicast neighbor 10.0.0.3 remote-as 65000 neighbor 10.0.0.3 update-source Loopback0 ! address-family vpnv4 neighbor 10.0.0.3 activate neighbor 10.0.0.3 send-community extended exit-address-family ! address-family ipv4 vrf VPN-USER-A neighbor 10.2.4.4 remote-as 65099 neighbor 10.2.4.4 activate neighbor 10.2.4.4 as-override exit-address-family ! end
hostname R3 ! vrf definition VPN-USER-A rd 65000:65099 route-target export 65000:65099 route-target import 65000:65099 ! address-family ipv4 exit-address-family ! interface Loopback0 ip address 10.0.0.3 255.255.255.255 ip ospf 1 area 0 ! interface FastEthernet0/0 ip address 10.1.3.3 255.255.255.0 ip ospf 1 area 0 no shutdown ! interface FastEthernet0/1 vrf forwarding VPN-USER-A ip address 10.3.5.3 255.255.255.0 no shutdown ! router ospf 1 mpls ldp autoconfig ! router bgp 65000 no bgp default ipv4-unicast neighbor 10.0.0.2 remote-as 65000 neighbor 10.0.0.2 update-source Loopback0 ! address-family vpnv4 neighbor 10.0.0.2 activate neighbor 10.0.0.2 send-community extended exit-address-family ! address-family ipv4 vrf VPN-USER-A neighbor 10.3.5.5 remote-as 65099 neighbor 10.3.5.5 activate neighbor 10.3.5.5 as-override exit-address-family ! end
hostname R4 ! interface FastEthernet0/0 ip address 10.2.4.4 255.255.255.0 no shutdown ! interface FastEthernet0/1 ip address 10.4.6.4 255.255.255.0 no shutdown ! router bgp 65099 no bgp default ipv4-unicast neighbor 10.2.4.2 remote-as 65000 neighbor 10.4.6.6 remote-as 65006 ! address-family ipv4 neighbor 10.2.4.2 activate neighbor 10.4.6.6 activate exit-address-family ! router bgp 65099 address-family ipv4 neighbor 10.4.6.6 allowas-in ! end
hostname R5 ! interface FastEthernet0/0 ip address 10.3.5.5 255.255.255.0 no shutdown ! router bgp 65099 no bgp default ipv4-unicast neighbor 10.3.5.3 remote-as 65000 ! address-family ipv4 neighbor 10.3.5.3 activate exit-address-family ! end
hostname R6 ! interface FastEthernet0/0 ip address 10.4.6.6 255.255.255.0 no shutdown ! interface FastEthernet0/1 ip address 10.6.8.6 255.255.255.0 no shutdown ! router bgp 65006 no bgp default ipv4-unicast neighbor 10.4.6.4 remote-as 65099 neighbor 10.6.8.8 remote-as 65099 ! address-family ipv4 neighbor 10.4.6.4 activate neighbor 10.6.8.8 activate exit-address-family ! end
hostname R8 ! interface Loopback0 ip address 10.0.0.8 255.255.255.255 ! interface FastEthernet0/0 ip address 10.6.8.8 255.255.255.0 no shutdown ! router bgp 65099 no bgp default ipv4-unicast neighbor 10.6.8.6 remote-as 65006 ! address-family ipv4 network 10.0.0.8 mask 255.255.255.255 neighbor 10.6.8.6 activate exit-address-family ! end
VERIFY
・R8のloopback を広報し、その見え方を確認
R8#sh ip bgp | b Network Network Next Hop Metric LocPrf Weight Path *> 10.0.0.8/32 0.0.0.0 0 32768 i R8#
R6#sh ip bgp | b Network Network Next Hop Metric LocPrf Weight Path *> 10.0.0.8/32 10.6.8.8 0 0 65099 i R6# R6#sh ip bgp nei 10.4.6.4 adv | b Network Network Next Hop Metric LocPrf Weight Path *> 10.0.0.8/32 10.6.8.8 0 0 65099 i Total number of prefixes 1 R6#
R4#sh ip bgp | b Network R4#
R4が同じAS番号なので破棄する。ここで無理やり受信させるためにallowas-in
R4(config)#router bgp 65099 R4(config-router)# address-family ipv4 R4(config-router-af)# neighbor 10.4.6.6 allowas-in R4(config-router-af)#end R4#clear R4#cle ip bgp * soft R4# R4#sh ip bgp | b Network Network Next Hop Metric LocPrf Weight Path *> 10.0.0.8/32 10.4.6.6 0 65006 65099 i R4#
R2#sh bgp vpnv4 uni all | b Network Network Next Hop Metric LocPrf Weight Path Route Distinguisher: 65000:65099 (default for vrf VPN-USER-A) *> 10.0.0.8/32 10.2.4.4 0 65099 65006 65099 i R2#
R3#sh bgp vpnv4 uni all | b Network Network Next Hop Metric LocPrf Weight Path Route Distinguisher: 65000:65099 (default for vrf VPN-USER-A) *>i10.0.0.8/32 10.0.0.2 0 100 0 65099 65006 65099 i R3#
さて、結果は・・・
R5#sh ip bgp | b Network Network Next Hop Metric LocPrf Weight Path *> 10.0.0.8/32 10.3.5.3 0 65000 65000 65006 65000 i R5#
非BGPネイバからの経路もASが上書きされてました。
コメント