From: ccie23 ccie23 (ccie2323@gmail.com)
Date: Sun Mar 30 2008 - 23:23:43 ART
Question.
5.1. BGP Peerings
Configure BGP AS 200 on R3.
Configure BGP AS 100 on R1, R2, and R6.
Configure BGP peerings between R1 & R2, R1 & R3, R1 & R6, R2 & R6,
R3 & BB2, and R6 & BB1.
The peering between R3 and BB2 should be authenticated with the
password CISCO.
Do not enable BGP on R5 or SW3.
All devices running BGP should have reachability to all BGP learned
prefixes.
Do not use tunelling to accomplish this.
Solution Guide
R1:
router bgp 100
neighbor 190.1.0.2 remote-as 100
neighbor 190.1.0.6 remote-as 100
neighbor 190.1.135.3 remote-as 200
R2:
router bgp 100
neighbor 190.1.135.1 remote-as 100
neighbor 190.1.0.6 remote-as 100
R3:
router bgp 200
neighbor 190.1.135.1 remote-as 100
neighbor 192.10.1.254 remote-as 254
neighbor 192.10.1.254 password CISCO
!
router ospf 1
redistribute bgp 200 subnets route-map BGP->OSPF
!
route-map BGP->OSPF permit 10
match as-path 1
!
ip as-path access-list 1 permit ^254_
R6:
router bgp 100
network 190.1.0.0 mask 255.255.255.0
aggregate-address 190.1.0.0 255.255.0.0 summary-only
neighbor 190.1.135.1 remote-as 100
neighbor 190.1.0.2 remote-as 100
neighbor 54.1.1.254 remote-as 54
!
router eigrp 10
redistribute bgp 100 metric 1 1 1 1 1 route-map BGP->EIGRP
distribute-list prefix BGP out Serial0/0/0.1
!
route-map BGP->EIGRP permit 10
match as-path 1
!
ip as-path access-list 1 permit ^54_
!
ip prefix-list BGP seq 5 deny 28.119.16.0/24
ip prefix-list BGP seq 10 deny 28.119.17.0/24
ip prefix-list BGP seq 15 deny 112.0.0.0/8
ip prefix-list BGP seq 20 deny 113.0.0.0/8
ip prefix-list BGP seq 25 deny 114.0.0.0/8
ip prefix-list BGP seq 30 deny 115.0.0.0/8
ip prefix-list BGP seq 35 deny 116.0.0.0/8
ip prefix-list BGP seq 40 deny 117.0.0.0/8
ip prefix-list BGP seq 45 deny 118.0.0.0/8
ip prefix-list BGP seq 50 deny 119.0.0.0/8
ip prefix-list BGP seq 55 permit 0.0.0.0/0 le 32
Task 5.1 Breakdown
When redistributing from BGP into IGP care needs to be taken to ensure that
only the BGP routes learned at the edge are redistributed. If all routes
were
redistributed from BGP into IGP, traffic could be blackholed. This can ocurr
by
follwing the lower administrative distance IGP over iBGP routes toward the
wrong
edge of the network.
On R6, if the routes redistributed from BGP into EIGRP are not filtered from
being advertised back to BB1, a routing loop will result. This will happen
because
BB1 would prefer the EIGRP routes rather than the BGP routes to BB2 where
the
routes are originated.
Finally, the task states that all device running BGP need reachability to
the
advertised routes which necessitates advertising the internal network space
to
AS 54. This is done using an aggregate route on R6.
My Question is why does the solution guide solve the task by redistributing
BGP into IGP? From what i understand its just a blackhole problem on R5. Am
i missing anything?
This archive was generated by hypermail 2.1.4 : Tue Apr 01 2008 - 07:53:54 ART