- If the link between R1 and R3 goes down traffic from AS 300 to AS 254 should be rerouted directly to AS 200.
The syntax for conditional advertisement is as follows:
neighbor <IP> advertise-map MAP1 {non-exist|exist-map} MAP2
The configuration involves defining two route-maps. One route-map (MAP1) selects the prefixes to be advertised to the peer. These prefixes must already exist in the local BGP table. The other route-map (MAP2) selects the prefixes to be tracked in the local BGP table. If this is a “non-exist” map, than condition is triggered when no prefixes in the BGP table match the route-map. If this is an
“exist” map, then condition is triggered when there is a prefix in the BGP table matching the route-map. BGP process performs condition verification every time BGP scanner runs (60 seconds by default) so it may take some time after your configuration change before the conditional advertisement occurs.
configuration:
R3:
ip as-path access-list 1 permit 254$
!
route-map ADVERTISE_MAP permit 10
match as-path 1
!
ip prefix-list LINK_R1_R3 permit 155.1.13.0/24
!
route-map NON_EXIST_MAP permit 10
match ip address prefix-list LINK_R1_R3
!
router bgp 200
network 155.1.13.0 mask 255.255.255.0
neighbor 155.1.37.7 advertise-map ADVERTISE_MAP non-exist-map NON_EXIST_MAP
verification:
normal condition:
Rack1R3#show ip bgp regexp 254$
BGP table version is 94, local router ID is 150.1.3.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* i205.90.31.0 192.10.1.254 0 100 0 254 ?
*>i 192.10.1.254 0 100 0 254 ?
* i220.20.3.0 192.10.1.254 0 100 0 254 ?
*>i 192.10.1.254 0 100 0 254 ?
* i222.22.2.0 192.10.1.254 0 100 0 254 ?
*>i 192.10.1.254 0 100 0 254 ?
Rack1R3#show ip bgp neighbors 155.1.37.7 advertised-routes
BGP table version is 94, local router ID is 150.1.3.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i10.0.0.0/24 155.1.23.2 0 100 0 i
*>i10.0.0.0/22 155.1.0.5 0 100 0 i
*>i10.0.1.0/24 155.1.23.2 0 100 0 i
*>i10.0.2.0/24 155.1.23.2 0 100 0 i
*>i10.0.3.0/24 155.1.23.2 0 100 0 i
*> 28.119.16.0/24 155.1.13.1 0 100 54 i
*> 28.119.17.0/24 155.1.13.1 0 100 54 i
*> 112.0.0.0 155.1.13.1 0 100 54 50 60 i
*> 113.0.0.0 155.1.13.1 0 100 54 50 60 i
*> 114.0.0.0 155.1.13.1 0 100 54 i
*> 115.0.0.0 155.1.13.1 0 100 54 i
*> 116.0.0.0 155.1.13.1 0 100 54 i
*> 117.0.0.0 155.1.13.1 0 100 54 i
*> 118.0.0.0 155.1.13.1 0 100 54 i
*> 119.0.0.0 155.1.13.1 0 100 54 i
*> 155.1.0.0 155.1.13.1 0 100 i
*> 155.1.13.0/24 0.0.0.0 0 32768 i
*>i222.22.0.0 155.1.23.2 0 100 0 i
*>i222.22.1.0 155.1.23.2 0 100 0 i
Rack1R3#show ip bgp neighbors 155.1.37.7
BGP neighbor is 155.1.37.7, remote AS 300, external link
BGP version 4, remote router ID 150.1.77.77
BGP state = Established, up for 02:12:44
Last read 00:00:15, last write 00:00:44, hold time is 180, keepalive interval is 60 seconds
Neighbor capabilities:
Route refresh: advertised and received(old & new)
Address family IPv4 Unicast: advertised and received
Message statistics:
InQ depth is 0
OutQ depth is 0
Sent Rcvd
Opens: 1 1
Notifications: 0 0
Updates: 52 31
Keepalives: 134 128
Route Refresh: 0 1
Total: 187 161
Default minimum time between advertisement runs is 30 seconds
For address family: IPv4 Unicast
BGP table version 94, neighbor version 94/0
Output queue size : 0
Index 4, Offset 0, Mask 0x10
4 update-group member
Inbound soft reconfiguration allowed
Community attribute sent to this neighbor
Condition-map NON_EXIST_MAP, Advertise-map ADVERTISE_MAP, status: Withdraw
Sent Rcvd
Prefix activity: ---- ----
Prefixes Current: 19 12 (Consumes 624 bytes)
Prefixes Total: 19 36
Implicit Withdraw: 19 12
Explicit Withdraw: 3 12
Used as bestpath: n/a 1
Used as multipath: n/a 0
Outbound Inbound
Local Policy Denied Prefixes: -------- -------
Suppressed duplicate: 0 12
AS_PATH loop: n/a 42
advertise-map: 6 n/a
Well-known Community: 3 n/a
Bestpath from this peer: 4 n/a
Total: 13 54
Number of NLRIs in the update sent: max 8, min 0
Connections established 1; dropped 0
Last reset never
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Connection is ECN Disabled, Mininum incoming TTL 0, Outgoing TTL 1
Local host: 155.1.37.3, Local port: 179
Foreign host: 155.1.37.7, Foreign port: 45858
Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
Event Timers (current time is 0x79FF68):
Timer Starts Wakeups Next
Retrans 151 0 0x0
TimeWait 0 0 0x0
AckHold 142 136 0x0
SendWnd 0 0 0x0
KeepAlive 0 0 0x0
GiveUp 0 0 0x0
PmtuAger 0 0 0x0
DeadWait 0 0 0x0
iss: 189714911 snduna: 189720443 sndnxt: 189720443 sndwnd: 15320
irs: 437617711 rcvnxt: 437621950 rcvwnd: 15280 delrcvwnd: 1104
SRTT: 300 ms, RTTO: 303 ms, RTV: 3 ms, KRTT: 0 ms
minRTT: 4 ms, maxRTT: 300 ms, ACK hold: 200 ms
Flags: passive open, nagle, gen tcbs
IP Precedence value : 6
Datagrams (max data segment is 1460 bytes):
Rcvd: 287 (out of order: 0), with data: 143, total data bytes: 4238
Sent: 291 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 0), with data: 152, total data bytes: 5550
BGP neighbor is 155.1.37.7, remote AS 300, external link
BGP version 4, remote router ID 150.1.77.77
BGP state = Established, up for 02:12:44
Last read 00:00:15, last write 00:00:44, hold time is 180, keepalive interval is 60 seconds
Neighbor capabilities:
Route refresh: advertised and received(old & new)
Address family IPv4 Unicast: advertised and received
Message statistics:
InQ depth is 0
OutQ depth is 0
Sent Rcvd
Opens: 1 1
Notifications: 0 0
Updates: 52 31
Keepalives: 134 128
Route Refresh: 0 1
Total: 187 161
Default minimum time between advertisement runs is 30 seconds
For address family: IPv4 Unicast
BGP table version 94, neighbor version 94/0
Output queue size : 0
Index 4, Offset 0, Mask 0x10
4 update-group member
Inbound soft reconfiguration allowed
Community attribute sent to this neighbor
Condition-map NON_EXIST_MAP, Advertise-map ADVERTISE_MAP, status: Withdraw
Sent Rcvd
Prefix activity: ---- ----
Prefixes Current: 19 12 (Consumes 624 bytes)
Prefixes Total: 19 36
Implicit Withdraw: 19 12
Explicit Withdraw: 3 12
Used as bestpath: n/a 1
Used as multipath: n/a 0
Outbound Inbound
Local Policy Denied Prefixes: -------- -------
Suppressed duplicate: 0 12
AS_PATH loop: n/a 42
advertise-map: 6 n/a
Well-known Community: 3 n/a
Bestpath from this peer: 4 n/a
Total: 13 54
Number of NLRIs in the update sent: max 8, min 0
Connections established 1; dropped 0
Last reset never
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Connection is ECN Disabled, Mininum incoming TTL 0, Outgoing TTL 1
Local host: 155.1.37.3, Local port: 179
Foreign host: 155.1.37.7, Foreign port: 45858
Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
Event Timers (current time is 0x79FF68):
Timer Starts Wakeups Next
Retrans 151 0 0x0
TimeWait 0 0 0x0
AckHold 142 136 0x0
SendWnd 0 0 0x0
KeepAlive 0 0 0x0
GiveUp 0 0 0x0
PmtuAger 0 0 0x0
DeadWait 0 0 0x0
iss: 189714911 snduna: 189720443 sndnxt: 189720443 sndwnd: 15320
irs: 437617711 rcvnxt: 437621950 rcvwnd: 15280 delrcvwnd: 1104
SRTT: 300 ms, RTTO: 303 ms, RTV: 3 ms, KRTT: 0 ms
minRTT: 4 ms, maxRTT: 300 ms, ACK hold: 200 ms
Flags: passive open, nagle, gen tcbs
IP Precedence value : 6
Datagrams (max data segment is 1460 bytes):
Rcvd: 287 (out of order: 0), with data: 143, total data bytes: 4238
Sent: 291 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 0), with data: 152, total data bytes: 5550
after shutting down the link between R1 and R3:
Rack1R3#show ip bgp neighbors 155.1.37.7 advertised-routes
BGP table version is 111, local router ID is 150.1.3.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i10.0.0.0/24 155.1.23.2 0 100 0 i
*>i10.0.0.0/22 155.1.0.5 0 100 0 i
*>i10.0.1.0/24 155.1.23.2 0 100 0 i
*>i10.0.2.0/24 155.1.23.2 0 100 0 i
*>i10.0.3.0/24 155.1.23.2 0 100 0 i
*>i28.119.16.0/24 155.1.45.4 0 100 0 100 54 i
*>i28.119.17.0/24 155.1.45.4 0 100 0 100 54 i
*>i112.0.0.0 155.1.45.4 0 100 0 100 54 50 60 i
*>i113.0.0.0 155.1.45.4 0 100 0 100 54 50 60 i
*>i114.0.0.0 155.1.45.4 0 100 0 100 54 i
*>i115.0.0.0 155.1.45.4 0 100 0 100 54 i
*>i116.0.0.0 155.1.45.4 0 100 0 100 54 i
*>i117.0.0.0 155.1.45.4 0 100 0 100 54 i
*>i118.0.0.0 155.1.45.4 0 100 0 100 54 i
*>i119.0.0.0 155.1.45.4 0 100 0 100 54 i
*>i155.1.0.0 155.1.45.4 0 100 0 100 i
*>i205.90.31.0 192.10.1.254 0 100 0 254 ?
*>i220.20.3.0 192.10.1.254 0 100 0 254 ?
*>i222.22.0.0 155.1.23.2 0 100 0 i
*>i222.22.1.0 155.1.23.2 0 100 0 i
*>i222.22.2.0 192.10.1.254 0 100 0 254 ?
BGP table version is 111, local router ID is 150.1.3.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i10.0.0.0/24 155.1.23.2 0 100 0 i
*>i10.0.0.0/22 155.1.0.5 0 100 0 i
*>i10.0.1.0/24 155.1.23.2 0 100 0 i
*>i10.0.2.0/24 155.1.23.2 0 100 0 i
*>i10.0.3.0/24 155.1.23.2 0 100 0 i
*>i28.119.16.0/24 155.1.45.4 0 100 0 100 54 i
*>i28.119.17.0/24 155.1.45.4 0 100 0 100 54 i
*>i112.0.0.0 155.1.45.4 0 100 0 100 54 50 60 i
*>i113.0.0.0 155.1.45.4 0 100 0 100 54 50 60 i
*>i114.0.0.0 155.1.45.4 0 100 0 100 54 i
*>i115.0.0.0 155.1.45.4 0 100 0 100 54 i
*>i116.0.0.0 155.1.45.4 0 100 0 100 54 i
*>i117.0.0.0 155.1.45.4 0 100 0 100 54 i
*>i118.0.0.0 155.1.45.4 0 100 0 100 54 i
*>i119.0.0.0 155.1.45.4 0 100 0 100 54 i
*>i155.1.0.0 155.1.45.4 0 100 0 100 i
*>i205.90.31.0 192.10.1.254 0 100 0 254 ?
*>i220.20.3.0 192.10.1.254 0 100 0 254 ?
*>i222.22.0.0 155.1.23.2 0 100 0 i
*>i222.22.1.0 155.1.23.2 0 100 0 i
*>i222.22.2.0 192.10.1.254 0 100 0 254 ?
Rack1R3#show ip bgp neighbors 155.1.37.7
BGP neighbor is 155.1.37.7, remote AS 300, external link
BGP version 4, remote router ID 150.1.77.77
BGP state = Established, up for 02:16:12
Last read 00:00:42, last write 00:00:12, hold time is 180, keepalive interval is 60 seconds
Neighbor capabilities:
Route refresh: advertised and received(old & new)
Address family IPv4 Unicast: advertised and received
Message statistics:
InQ depth is 0
OutQ depth is 0
Sent Rcvd
Opens: 1 1
Notifications: 0 0
Updates: 58 31
Keepalives: 138 131
Route Refresh: 0 1
Total: 197 164
Default minimum time between advertisement runs is 30 seconds
For address family: IPv4 Unicast
BGP table version 111, neighbor version 108/0
Output queue size : 0
Index 4, Offset 0, Mask 0x10
4 update-group member
Inbound soft reconfiguration allowed
Community attribute sent to this neighbor
Condition-map NON_EXIST_MAP, Advertise-map ADVERTISE_MAP, status: Advertise
Sent Rcvd
Prefix activity: ---- ----
Prefixes Current: 18 12 (Consumes 624 bytes)
Prefixes Total: 31 36
Implicit Withdraw: 30 12
Explicit Withdraw: 5 12
Used as bestpath: n/a 1
Used as multipath: n/a 0
Outbound Inbound
Local Policy Denied Prefixes: -------- -------
Suppressed duplicate: 0 12
AS_PATH loop: n/a 42
advertise-map: 6 n/a
Well-known Community: 3 n/a
Bestpath from this peer: 4 n/a
Total: 13 54
Number of NLRIs in the update sent: max 8, min 0
Connections established 1; dropped 0
Last reset never
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Connection is ECN Disabled, Mininum incoming TTL 0, Outgoing TTL 1
Local host: 155.1.37.3, Local port: 179
Foreign host: 155.1.37.7, Foreign port: 45858
Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
Event Timers (current time is 0x7D288C):
Timer Starts Wakeups Next
Retrans 159 0 0x0
TimeWait 0 0 0x0
AckHold 146 140 0x0
SendWnd 0 0 0x0
KeepAlive 0 0 0x0
GiveUp 0 0 0x0
PmtuAger 0 0 0x0
DeadWait 0 0 0x0
iss: 189714911 snduna: 189720871 sndnxt: 189720871 sndwnd: 16384
irs: 437617711 rcvnxt: 437622042 rcvwnd: 15188 delrcvwnd: 1196
SRTT: 300 ms, RTTO: 303 ms, RTV: 3 ms, KRTT: 0 ms
minRTT: 4 ms, maxRTT: 300 ms, ACK hold: 200 ms
Flags: passive open, nagle, gen tcbs
IP Precedence value : 6
Datagrams (max data segment is 1460 bytes):
Rcvd: 298 (out of order: 0), with data: 147, total data bytes: 4330
Sent: 302 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 0), with data: 159, total data bytes: 5959
BGP neighbor is 155.1.37.7, remote AS 300, external link
BGP version 4, remote router ID 150.1.77.77
BGP state = Established, up for 02:16:12
Last read 00:00:42, last write 00:00:12, hold time is 180, keepalive interval is 60 seconds
Neighbor capabilities:
Route refresh: advertised and received(old & new)
Address family IPv4 Unicast: advertised and received
Message statistics:
InQ depth is 0
OutQ depth is 0
Sent Rcvd
Opens: 1 1
Notifications: 0 0
Updates: 58 31
Keepalives: 138 131
Route Refresh: 0 1
Total: 197 164
Default minimum time between advertisement runs is 30 seconds
For address family: IPv4 Unicast
BGP table version 111, neighbor version 108/0
Output queue size : 0
Index 4, Offset 0, Mask 0x10
4 update-group member
Inbound soft reconfiguration allowed
Community attribute sent to this neighbor
Condition-map NON_EXIST_MAP, Advertise-map ADVERTISE_MAP, status: Advertise
Sent Rcvd
Prefix activity: ---- ----
Prefixes Current: 18 12 (Consumes 624 bytes)
Prefixes Total: 31 36
Implicit Withdraw: 30 12
Explicit Withdraw: 5 12
Used as bestpath: n/a 1
Used as multipath: n/a 0
Outbound Inbound
Local Policy Denied Prefixes: -------- -------
Suppressed duplicate: 0 12
AS_PATH loop: n/a 42
advertise-map: 6 n/a
Well-known Community: 3 n/a
Bestpath from this peer: 4 n/a
Total: 13 54
Number of NLRIs in the update sent: max 8, min 0
Connections established 1; dropped 0
Last reset never
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Connection is ECN Disabled, Mininum incoming TTL 0, Outgoing TTL 1
Local host: 155.1.37.3, Local port: 179
Foreign host: 155.1.37.7, Foreign port: 45858
Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
Event Timers (current time is 0x7D288C):
Timer Starts Wakeups Next
Retrans 159 0 0x0
TimeWait 0 0 0x0
AckHold 146 140 0x0
SendWnd 0 0 0x0
KeepAlive 0 0 0x0
GiveUp 0 0 0x0
PmtuAger 0 0 0x0
DeadWait 0 0 0x0
iss: 189714911 snduna: 189720871 sndnxt: 189720871 sndwnd: 16384
irs: 437617711 rcvnxt: 437622042 rcvwnd: 15188 delrcvwnd: 1196
SRTT: 300 ms, RTTO: 303 ms, RTV: 3 ms, KRTT: 0 ms
minRTT: 4 ms, maxRTT: 300 ms, ACK hold: 200 ms
Flags: passive open, nagle, gen tcbs
IP Precedence value : 6
Datagrams (max data segment is 1460 bytes):
Rcvd: 298 (out of order: 0), with data: 147, total data bytes: 4330
Sent: 302 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 0), with data: 159, total data bytes: 5959
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