Topology:
Use configuration from BGP task #4 as initial configuration for this task.
Requirements:
1. Configure AS12, so it will only install BGP routes with AS-PATH shorter than 10.
2 R5 should only advertise default-route to AS12, if R5 has reachability to prefix 67.0/16.
3 AS12 should prefer using AS5 to reach prefix 1.0/16. You are only allowed to configure R5 to achieve this requirement.
Solution:
Highlight the text below to reveal the solution.
This task requires knowledge of BGP conditional advertisement and conditional injection features.
Requirement #1 - in IOS, use "bgp maxas-limit" command. in IOS-XR, configure route-policy to match on as-path length.
Requirement #2 - on R5, configure conditional advertisement, using advertise-map / exist-map. Note feature does not seem to be supported in IOS-XR.
Requirement #3 - on R5, configure conditional route injection. Advertise to AS12 longer prefixes of aggregate 1.0/16. Note feature not supported on ASR9K.
This task requires knowledge of BGP conditional advertisement and conditional injection features.
Requirement #1 - in IOS, use "bgp maxas-limit" command. in IOS-XR, configure route-policy to match on as-path length.
Requirement #2 - on R5, configure conditional advertisement, using advertise-map / exist-map. Note feature does not seem to be supported in IOS-XR.
Requirement #3 - on R5, configure conditional route injection. Advertise to AS12 longer prefixes of aggregate 1.0/16. Note feature not supported on ASR9K.
Verification:
R1:
!
router bgp 12
bgp log-neighbor-changes
bgp maxas-limit 10
neighbor IBGP peer-group
neighbor IBGP remote-as 12
neighbor IBGP update-source Loopback0
neighbor IBGP send-community
neighbor 5.0.15.5 remote-as 5
neighbor 5.0.15.5 route-map LAST out
neighbor 12.0.2.2 peer-group IBGP
neighbor 12.0.3.3 peer-group IBGP
neighbor 12.0.4.4 peer-group IBGP
!
R3:
!
route-policy PRIMARY_IN
if as-path length ge 10 then
drop
endif
if destination in AS8 then
set local-preference 300
else
pass
endif
end-policy
!
route-policy SECONDARY_IN
if as-path length ge 10 then
drop
endif
if destination in AS8 then
set local-preference 200
else
pass
endif
end-policy
!
router bgp 12
address-family ipv4 unicast
!
neighbor-group IBGP
remote-as 12
update-source Loopback0
address-family ipv4 unicast
!
!
neighbor 12.0.1.1
use neighbor-group IBGP
!
neighbor 12.0.2.2
use neighbor-group IBGP
!
neighbor 12.0.4.4
use neighbor-group IBGP
!
neighbor 67.0.36.6
remote-as 67
address-family ipv4 unicast
route-policy SECONDARY_IN in
route-policy SECONDARY_OUT out
!
!
neighbor 67.0.37.7
remote-as 67
address-family ipv4 unicast
route-policy PRIMARY_IN in
route-policy BGP_ALL out
!
!
!
R5:
!
ip prefix-list AGGREGATE seq 5 permit 1.0.0.0/16
!
ip prefix-list ORIGINATE seq 5 permit 1.0.0.0/17
ip prefix-list ORIGINATE seq 10 permit 1.0.128.0/17
!
ip prefix-list DEF seq 5 permit 0.0.0.0/0
!
ip prefix-list SOURCE seq 5 permit 8.0.58.8/32
!
route-map INJECT permit 100
set ip address prefix-list ORIGINATE
!
route-map EXIST permit 100
match ip address prefix-list AGGREGATE
match ip route-source SOURCE
!
route-map ADVMAP permit 100
match ip address prefix-list DEF
!
route-map NO_TRANSIT permit 100
set community no-export
!
route-map NONEXIST permit 100
match ip address prefix-list AS67
!
router bgp 5
bgp log-neighbor-changes
bgp inject-map INJECT exist-map EXIST copy-attributes
network 5.0.0.0 mask 255.255.0.0
neighbor 5.0.15.1 remote-as 12
neighbor 5.0.15.1 send-community
neighbor 5.0.15.1 route-map NO_TRANSIT out
neighbor 5.0.15.1 advertise-map ADVMAP exist-map NONEXIST
neighbor 8.0.58.8 remote-as 8
neighbor 8.0.58.8 password STRONG
!
