Implemented as per the feature description given in the source link.
Descriprion:
The BGP conditional advertisement feature uses the non-exist-map or exist-map
and the advertise-map keywords of the neighbor advertise-map command in order
to track routes by the route prefix.
non-exist-map :
If a route prefix is not present in output of the non-exist-map command, then
the route specified by the advertise-map command is announced.
exist-map :
If a route prefix is present in output of the exist-map command, then the route
specified by the advertise-map command is announced.
The conditional BGP announcements are sent in addition to the normal
announcements that a BGP router sends to its peers.
The conditional advertisement process is triggered by the BGP scanner process,
which runs every 60 seconds. This means that the maximum time for the conditional
advertisement to take effect is 60 seconds. The conditional advertisement can take
effect sooner, depending on when the tracked route is removed from the BGP table
and when the next instance of the BGP scanner occurs.
Sample Configuration on DUT
---------------------------
Router2# show running-config
Building configuration...
Withdraw when non-exist-map prefixes present in BGP table:
----------------------------------------------------------
Router2# show ip bgp all wide
For address family: IPv4 Unicast
BGP table version is 8, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.0/24 10.10.10.1 0 0 1 i
*> 2.2.2.0/24 0.0.0.0 0 32768 i
*> 3.3.3.0/24 10.10.20.3 0 0 3 i
*> 200.200.0.0/16 0.0.0.0 0 32768 i
Displayed 4 routes and 4 total paths
For address family: IPv6 Unicast
BGP table version is 8, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 2001:db8::1/128 fe80::a00:27ff:fecb:ad57 0 0 1 i
*> 2001:db8::2/128 :: 0 32768 i
*> 2001:db8::3/128 fe80::a00:27ff:fe76:6738 0 0 3 i
*> 2001:db8::200/128 :: 0 32768 i
Displayed 4 routes and 4 total paths
Router2#
Router2# show ip bgp neighbors 10.10.10.1
BGP neighbor is 10.10.10.1, remote AS 1, local AS 2, external link
!--- Output suppressed.
For address family: IPv4 Unicast
Update group 9, subgroup 5
Packet Queue length 0
Inbound soft reconfiguration allowed
Community attribute sent to this neighbor(all)
Condition NON_EXIST, Condition-map *CONDITION, Advertise-map *ADVERTISE, status: Withdraw
1 accepted prefixes
For address family: IPv6 Unicast
Update group 10, subgroup 6
Packet Queue length 0
Inbound soft reconfiguration allowed
Community attribute sent to this neighbor(all)
Condition NON_EXIST, Condition-map *CONDITION_6, Advertise-map *ADVERTISE_6, status: Withdraw
1 accepted prefixes
!--- Output suppressed.
Router2#
Here 2.2.2.0/24 & 200.200.0.0/16 (prefixes in advertise-map) are withdrawn
by conditional advertisement scanner as the prefix(3.3.3.0/24) specified
by non-exist-map is present in BGP table.
Router2# show ip bgp all neighbors 10.10.10.1 advertised-routes wide
For address family: IPv4 Unicast
BGP table version is 8, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.0/24 0.0.0.0 0 1 i
*> 3.3.3.0/24 0.0.0.0 0 3 i
Total number of prefixes 2
For address family: IPv6 Unicast
BGP table version is 8, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 2001:db8::1/128 :: 0 1 i
*> 2001:db8::3/128 :: 0 3 i
*> 2001:db8::200/128 :: 0 32768 i
Total number of prefixes 3
Router2#
Advertise when non-exist-map prefixes not present in BGP table:
---------------------------------------------------------------
After Removing 3.3.3.0/24 (prefix present in non-exist-map),
2.2.2.0/24 & 200.200.0.0/16 (prefixes present in advertise-map) are advertised
Router2# show ip bgp all wide
For address family: IPv4 Unicast
BGP table version is 9, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.0/24 10.10.10.1 0 0 1 i
*> 2.2.2.0/24 0.0.0.0 0 32768 i
*> 200.200.0.0/16 0.0.0.0 0 32768 i
Displayed 3 routes and 3 total paths
For address family: IPv6 Unicast
BGP table version is 9, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 2001:db8::1/128 fe80::a00:27ff:fecb:ad57 0 0 1 i
*> 2001:db8::2/128 :: 0 32768 i
*> 2001:db8::200/128 :: 0 32768 i
Displayed 3 routes and 3 total paths
Router2#
Router2# show ip bgp neighbors 10.10.10.1
!--- Output suppressed.
For address family: IPv4 Unicast
Update group 9, subgroup 5
Packet Queue length 0
Inbound soft reconfiguration allowed
Community attribute sent to this neighbor(all)
Condition NON_EXIST, Condition-map *CONDITION, Advertise-map *ADVERTISE, status: Advertise
1 accepted prefixes
For address family: IPv6 Unicast
Update group 10, subgroup 6
Packet Queue length 0
Inbound soft reconfiguration allowed
Community attribute sent to this neighbor(all)
Condition NON_EXIST, Condition-map *CONDITION_6, Advertise-map *ADVERTISE_6, status: Advertise
1 accepted prefixes
!--- Output suppressed.
Router2#
Router2# show ip bgp all neighbors 10.10.10.1 advertised-routes wide
For address family: IPv4 Unicast
BGP table version is 9, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.0/24 0.0.0.0 0 1 i
*> 2.2.2.0/24 0.0.0.0 0 32768 i
*> 200.200.0.0/16 0.0.0.0 0 32768 i
Total number of prefixes 3
For address family: IPv6 Unicast
BGP table version is 9, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 2001:db8::1/128 :: 0 1 i
*> 2001:db8::2/128 :: 0 32768 i
*> 2001:db8::200/128 :: 0 32768 i