BGP ORF

初期設定

bgp_orf.txt

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before

iosv-3#sh ip bgp | b Origin
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

 Network          Next Hop            Metric LocPrf Weight Path

*>   1.1.1.1/32       150.1.23.2                             0 100 i
*>   2.2.2.2/32       150.1.23.2               0             0 100 i
*>   10.10.10.10/32   150.1.23.2                             0 100 200 i

prefix-list設定（iosv-3）

#prefix-list作成
iosv-3(config)#ip prefix-list ORF deny 10.10.10.10/32
iosv-3(config)#ip prefix-list ORF permit 0.0.0.0/0 le 32

#prefix-listの適用
iosv-3(config)#router bgp 300
iosv-3(config-router)#neighbor 150.1.23.2 prefix-list ORF in

#bgpプロセスの再起動
iosv-3(config-router)#do clear ip bgp *
*Jul  6 12:04:17.301: %BGP-3-NOTIFICATION_MANY: sent to 1 sessions 6/4 (Administrative Reset) for all peers
*Jul  6 12:04:17.327: %BGP-5-ADJCHANGE: neighbor 150.1.23.2 Down User reset
*Jul  6 12:04:17.328: %BGP_SESSION-5-ADJCHANGE: neighbor 150.1.23.2 IPv4 Unicast topology base removed from session  User reset
*Jul  6 12:04:25.485: %BGP-5-ADJCHANGE: neighbor 150.1.23.2 Up

#確認
iosv-3(config-router)#do sh ip bgp sum
<略>
BGP activity 5/3 prefixes, 5/3 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
150.1.23.2      4          100       7       4        3    0    0 00:00:07        2

iosv-3(config-router)#do sh ip bgp
<略>
RPKI validation codes: V valid, I invalid, N Not found

 Network          Next Hop            Metric LocPrf Weight Path

*>   1.1.1.1/32       150.1.23.2                             0 100 i
*>   2.2.2.2/32       150.1.23.2               0             0 100 i

10.10.10.10/32が消えた。しかし、

iosv-2#sh ip bgp neighbor 150.1.23.3 advertised-routes
BGP table version is 4, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
x best-external, a additional-path, c RIB-compressed,
t secondary path,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

 Network          Next Hop            Metric LocPrf Weight Path

r>i  1.1.1.1/32       150.1.12.1               0    100      0 i
*>   2.2.2.2/32       0.0.0.0                  0         32768 i
r>i  10.10.10.10/32   150.1.12.1               0    100      0 200 i

Total number of prefixes 3 

iosv-2は依然としてiosv-3へ向けて10.10.10.10/32を広告し続けている。これでは帯域が勿体ない。

ORF(Outbound Route Filtering)

iosv-2(config-router)#neighbor 150.1.23.3 capability orf prefix-list receive
iosv-3(config-router)#neighbor 150.1.23.2 capability orf prefix-list send

↑設定　確認↓

iosv-2#sh run | sec bgp                                
router bgp 100
 bgp log-neighbor-changes
 network 2.2.2.2 mask 255.255.255.255
 neighbor 150.1.12.1 remote-as 100
 neighbor 150.1.12.1 next-hop-self
 neighbor 150.1.23.3 remote-as 300
 neighbor 150.1.23.3 capability orf prefix-list receive

iosv-2#sh ip bgp neighbor 150.1.23.3 advertised-routes
<略>
 Network          Next Hop            Metric LocPrf Weight Path

r>i  1.1.1.1/32       150.1.12.1               0    100      0 i
*>   2.2.2.2/32       0.0.0.0                  0         32768 i

Total number of prefixes 2 

isov-2にはprefix-listが設定されていないけど、iosv-3からprefix-listの情報を受け取ってフィルタリングを行っている。

iosv-2#sh ip bgp neighbor 150.1.23.3 received prefix-filter
Address family: IPv4 Unicast
ip prefix-list 150.1.23.3: 2 entries
seq 5 deny 10.10.10.10/32
seq 10 permit 0.0.0.0/0 le 32