ルートテーブルとピアの安定性を保証するために(つまり、エクスポートされるRIBが再計算され、状態が変化してしま うのを回避するために)、インターネットコミュニティは、いくつかの標準機能を開発しました。その一例がダンピン グ (RFC 2439)です。ダンピングを用いると、頻繁なルートフラッピングに起因するRIBの再計算とそれによるピア の状態変化を避けることができます。ダンピングは、ルートが繰り返しフラッピングする場合に、一旦それが削除され、
まもなくしてからそれを元に戻るように保証します。ダンプされたルートは、ユーザが設定した時間の間、非アクティ ブな状態になります。この抑制状態の間、ルーターは抑制されたルートを隣接ルーターにアドバタイズしません。その 結果、安定性が維持されます。ルートフラッピングが頻繁なほど、抑制時間は長くなります。
注
ダンピングはEBGPのみに効力を持ち、IBGP (as-path
がヌル)は対象外です。ただし、コンフェデレーションの境界にダンピングを提供することができます。
IOSダンピングコンフィグレーションの例
以下の例は、RIPEに基づくCiscoルーターのダンピングコンフィグレーションの一部です。
!
router bgp 1111 no synchronization bgp router-id 1.1.1.4 bgp log-neighbor-changes bgp deterministic-med
bgp dampening route-map damp
aggregate-address 100.100.0.0 255.255.0.0 summary-only aggregate-address 100.200.0.0 255.255.0.0 summary-only timers bgp 30 90
neighbor internal peer-group neighbor internal remote-as 1111
neighbor internal update-source Loopback0 neighbor internal next-hop-self
neighbor internal soft-reconfiguration inbound neighbor external peer-group
neighbor external prefix-list martians in neighbor external route-map int_policy in neighbor external route-map ext_policy out neighbor external soft-reconfiguration inbound neighbor 1.1.1.1 peer-group internal
neighbor 1.1.1.6 peer-group internal neighbor 194.68.128.22 remote-as 2222 neighbor 194.68.128.22 peer-group external neighbor 194.68.128.33 remote-as 3333
この例は、ダンプジェネレータから100のプリフィックスを学習したCisco BGPテーブルを示しています。
neighbor 194.68.128.33 peer-group external no auto-summary
!
!
ip as-path access-list 10 permit ^$
!
!
ip prefix-list root_dns seq 1 permit 198.41.0.0/24 ip prefix-list root_dns seq 2 permit 128.9.0.0/16 ip prefix-list root_dns seq 3 permit 192.33.4.0/24 ip prefix-list root_dns seq 4 permit 128.8.0.0/16 ip prefix-list root_dns seq 5 permit 192.203.230.0/24 ip prefix-list root_dns seq 6 permit 192.5.4.0/23 ip prefix-list root_dns seq 7 permit 192.112.36.0/24 ip prefix-list root_dns seq 8 permit 128.63.0.0/16 ip prefix-list root_dns seq 9 permit 192.36.148.0/24 ip prefix-list root_dns seq 10 permit 193.0.14.0/24 ip prefix-list root_dns seq 11 permit 198.32.64.0/24 ip prefix-list root_dns seq 12 permit 202.12.27.0/24 route-map damp deny 1
match as-path 10
!
route-map damp deny 2
match ip address prefix-list root_dns
!
route-map damp permit 3 set dampening 15 750 2000 60
!
cisco_border#sh ip bgp sum
BGP router identifier 1.1.1.4, local AS number 1111 BGP table version is 117, main routing table version 117 111 network entries and 112 paths using 14799 bytes of memory 21 BGP path attribute entries using 1092 bytes of memory 2 BGP rrinfo entries using 48 bytes of memory
11 BGP AS-PATH entries using 376 bytes of memory 7 BGP community entries using 168 bytes of memory
25 BGP route-map cache entries using 400 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory Dampening enabled. 0 history paths, 0 dampened paths
BGP activity 243/968 prefixes, 247/135 paths, scan interval 15 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
1.1.1.1 4 1111 1015 1167 117 0 0 00:01:29 8
1.1.1.6 4 1111 949 1168 117 0 0 00:01:29 1
194.68.128.22 4 2222 2129 1036 117 0 0 00:00:52 100 194.68.128.33 4 3333 1013 987 117 0 0 00:01:14 1 cisco_border#
Partial route-table:
cisco_border#sh ip bgp
BGP table version is 117, local router ID is 1.1.1.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete
このコードは、ダンピングイベントのデバッグを示しています。
Network Next Hop Metric LocPrf Weight Path
*> 3.3.0.0/16 194.68.128.33 1 101 0 3333 i
*> 34.1.1.0/24 194.68.128.22 1622 0 2222 53285 33299 51178 {27016,57039,16690} e
*> 34.1.2.0/24 194.68.128.22 1622 0 2222 53285 33299 51178 {27016,57039,16690} e
*> 34.1.3.0/24 194.68.128.22 1622 0 2222 53285 33299 51178 {27016,57039,16690} e
*> 34.1.4.0/24 194.68.128.22 1622 0 2222 53285 33299 51178 {27016,57039,16690} e
*> 34.1.5.0/24 194.68.128.22 1622 0 2222 53285 33299 51178 {27016,57039,16690} e
*> 34.1.6.0/24 194.68.128.22 1622 0 2222 53285 33299 51178 {27016,57039,16690} e
*> 34.1.7.0/24 194.68.128.22 1622 0 2222 53285 33299 51178 {27016,57039,16690} e
*> 34.1.8.0/24 194.68.128.22 1622 0 2222 53285 33299 51178 {27016,57039,16690} e
*> 34.1.9.0/24 194.68.128.22 1622 0 2222 53285 33299 51178 {27016,57039,16690} e
*> 34.1.10.0/24 194.68.128.22 1622 0 2222 53285 33299 51178 {27016,57039,16690} e
*> 34.1.11.0/24 194.68.128.22 2563 0 2222 59294 21396 25638 36040 {18917,28575,47361} e
cisco_border#
cisco_border#debug ip bgp damp
*Mar 1 07:59:59.798: BGP(0): charge penalty for 34.1.37.0/24 path 2222 4482 46350 49469 25721 33830 {51019} with halflife-time 15 reuse/suppress 750/2000
*Mar 1 07:59:59.802: BGP(0): flapped 1 times since 00:00:00. New penalty is 1000
*Mar 1 08:00:00.814: BGP(0): charge penalty for 34.1.47.0/24 path 2222 11885 8653 38033 34606 with halflife-time 15 reuse/suppress 750/2000
*Mar 1 08:00:00.818: BGP(0): flapped 2 times since 00:00:16. New penalty is 1988
*Mar 1 08:00:01.810: BGP(0): charge penalty for 34.1.53.0/24 path 2222 24193 29338 1945 65275 {10312,4520} with halflife-time 15 reuse/suppress 750/2000
*Mar 1 08:00:01.814: BGP(0): flapped 1 times since 00:00:00. New penalty is 1000
*Mar 1 08:00:02.798: BGP(0): charge penalty for 34.1.13.0/24 path 2222 59294 21396 25638 36040 {18917,28575,47361} with halflife-time 15 reuse/suppress 750/2000
*Mar 1 08:00:02.802: BGP(0): flapped 1 times since 00:00:00. New penalty is 1000g all
*Mar 1 08:00:03.806: BGP(0): charge penalty for 34.1.7.0/24 path 2222 53285 33299 51178 {27016,57039,16690} with halflife-time 15
reuse/suppress 750/2000
*Mar 1 08:00:03.810: BGP(0): flapped 1 times since 00:00:00. New penalty is 1000
cisco_border#no debug all
All possible debugging has been turned off
このコードはダンプルートを示しています。
JUNOSダンピングコンフィグレーションの例
この例は、同じ結果をもたらすJUNOSソフトウェアのダンピングコンフィグレーションの一部を示しています。
cisco_border#sh ip bgp damp
BGP table version is 1001, local router ID is 1.1.1.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete
Network From Reuse Path
*d 34.1.2.0/24 194.68.128.22 00:21:10 2222 53285 33299 51178 {27016,57039,16690} e
[edit protocols bgp]
lunkan@lena# show traceoptions {
file bgp;
flag damping detail;
}
log-updown;
group external { type external;
local-address 194.68.128.2;
damping;
import ebgp_in;# /* Policy for inbound EBGP ( Damping etcÖ).
No damp on internal routes can happenÖ */
export ebgp;
neighbor 194.68.128.22 { peer-as 2222;
}
neighbor 194.68.128.33 { peer-as 3333;
} }
group internal { type internal;
local-address 1.1.1.2;
export internal;
neighbor 1.1.1.1 {
authentication-key "$9$-Xds4UjqQF/ZUjqPQ9C";
}
neighbor 1.1.1.6;
} }
policy-statement ebgp_in { term 1918 {
from {
route-filter 0.0.0.0/0 exact;
route-filter 10.0.0.0/8 orlonger;
route-filter 127.0.0.0/8 orlonger;
route-filter 192.168.0.0/16 orlonger;
}
then reject;
}
term local_pref {
from as-path from_pagent;
then {
local-preference 101;
}
以下は、35本のルートがダンピング状態にあるユニキャストテーブル(BGPテーブル)を要約したものです。
from {
route-filter 198.41.0.0/24 exact;
route-filter 128.9.0.0/16 exact;
route-filter 192.33.4.0/24 exact;
route-filter 128.8.0.0/16 exact;
route-filter 192.203.230.0/24 exact;
route-filter 192.5.4.0/23 exact;
route-filter 128.63.0.0/16 exact;
route-filter 192.36.148.0/24 exact;
route-filter 193.0.14.0/24 exact;
route-filter 198.32.64.0/24 exact;
route-filter 202.12.27.0/24 exact;
} then {
damping no;
accept;
} term damp {
then damping yes;/* Damping apply of rest of routes */
} }
damping no { disable;
}
damping yes { half-life 15;
reuse 750;
suppress 2000;
max-suppress 60;
} }
[edit protocols bgp]
lunkan@lena#
[edit protocols bgp]
lunkan@lena# run show bgp summary Groups: 3 Peers: 4 Down Peers: 0
Table Tot Paths Act Paths Suppressed History Damp State Pending
inet.0 113 9 35 101 101
0
inet.2 0 0 0 0 0
0
Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn
State|#Active/Received/Damped...
194.68.128.22 2222 1 6 0 29 00:00:05
0/101/35 0/0/0
194.68.128.33 3333 37 36 0 4 00:15:23
1/3/0 0/0/0
1.1.1.1 1111 388 461 0 1 00:15:27
7/8/0 0/0/0
1.1.1.6 1111 34 461 0 1 00:15:33
1/1/0 0/0/0
このコード例は、ダンピングのトレースを示しています。
このコード例は、ダンピングのモニタリングを示しています。
このコードは、ダンプルートからの出力を示しています。
[edit protocols bgp traceoptions]
lunkan@lena# show file bgp;
flag damping;
lunkan@lena# run monitor start bgp
Jan 11 02:18:36 bgp_damp_change: Change event Jan 11 02:18:36 bgp_dampen: Damping 34.1.1.0
Jan 11 02:18:36 bgp_rt_change: Dampening makes route unusable Jan 11 02:18:36 bgp_damp_change: Change event
Jan 11 02:18:36 bgp_dampen: Damping 34.1.2.0
Jan 11 02:18:36 bgp_rt_change: Dampening makes route unusable Jan 11 02:18:36 bgp_damp_change: Change event
Jan 11 02:18:36 bgp_dampen: Damping 34.1.3.0
Jan 11 02:18:36 bgp_rt_change: Dampening makes route unusable Jan 11 02:18:36 bgp_damp_change: Change event
Jan 11 02:18:36 bgp_dampen: Damping 34.1.4.0
Jan 11 02:18:36 bgp_rt_change: Dampening makes route unusable Jan 11 02:18:36 bgp_damp_change: Change event
Jan 11 02:18:36 bgp_dampen: Damping 34.1.5.0
Jan 11 02:18:36 bgp_rt_change: Dampening makes route unusable Jan 11 02:18:36 bgp_damp_change: Change event
lunkan@lena# run show route damping suppressed
inet.0: 125 destinations, 125 routes (22 active, 0 holddown, 103 hidden) + = Active Route, - = Last Active, * = Both
34.1.1.0/24 [BGP] 00:00:19, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.2.0/24 [BGP] 00:00:19, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.3.0/24 [BGP] 00:00:19, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.4.0/24 [BGP] 00:00:19, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.5.0/24 [BGP] 00:00:19, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.6.0/24 [BGP] 00:00:19, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.7.0/24 [BGP] 00:00:03, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.8.0/24 [BGP] 00:00:19, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
この例は、ダンピングヒストリ内のすべてのルートを示しています。
ダンプルートの出力の詳細は、次のとおりです。
lunkan@lena# run show route damping history
inet.0: 125 destinations, 125 routes (22 active, 0 holddown, 103 hidden) + = Active Route, - = Last Active, * = Both
34.1.1.0/24 [BGP] 00:00:43, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.2.0/24 [BGP] 00:00:43, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.3.0/24 [BGP] 00:00:43, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.4.0/24 [BGP] 00:00:43, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.5.0/24 [BGP] 00:00:36, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.6.0/24 [BGP] 00:00:15, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.7.0/24 [BGP] 00:00:43, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.8.0/24 [BGP] 00:00:43, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.9.0/24 [BGP] 00:00:43, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
> to 194.68.128.22 via fxp1.0
34.1.10.0/24 [BGP] 00:00:43, MED 1622, localpref 100
AS path: 2222 53285 33299 51178 {16690 27016 57039} E
lunkan@lena# run show route damping history detail
inet.0: 125 destinations, 125 routes (22 active, 0 holddown, 103 hidden) + = Active Route, - = Last Active, * = Both
34.1.1.0/24 (1 entry, 0 announced) BGP Preference: /-101
Nexthop: 194.68.128.22 via fxp1.0, selected State: <Hidden Ext>
Local AS: 1111 Peer AS: 2222 Age: 42 Metric: 1622
Task: BGP_2222.194.68.128.22+11000
AS path: 2222 53285 33299 51178 {16690 27016 57039} E Localpref: 100
Router ID: 194.68.128.22
Merit (last update/now): 12110/12110 Damping parameters: "yes"
Last update: 00:00:01 First update: 00:06:21 Flaps: 21
Suppressed. Reusable in: 00:59:40 Preference will be: 170
History entry. Expires in: 00:59:40