bgp announce /24

Answered Question
Jul 18th, 2007
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hi


we re-config the bgp and we would like to have as following:


for provider A

200.1.0.0/24

200.1.1.0/24

200.1.2.0/23


for provider B

200.1.0.0/24

200.1.1.0/24

200.1.2.0/24

200.1.3.0/24


we find that the router always announces /23 to provider B. How do we send four routes? pls advice



----


router bgp 30x

!

network 200.1.0.0

network 200.1.1.0

network 200.1.2.0 mask 255.255.254.0


neighbor 202.1.1.1 route-map Set_ASN_PB out

!

ip route 200.1.2.0 mask 255.255.254.0 null0 250

!

!

!

access-list 20 permit 200.1.0.0 0.0.0.255

access-list 20 permit 200.1.1.0 0.0.0.255

access-list 20 permit 200.1.2.0 0.0.0.255

access-list 20 permit 200.1.3.0 0.0.0.255



!

ip as-path access-list 130 deny .*

ip as-path access-list 130 permit ^$

!

!

route-map Set_ASN_PB permit 10

match ip address 20

!

route-map Set_ASN_PB permit 30

match as-path 130

!


---

BGP table version is 248, local router ID is 10.254.210.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

Origin codes: i - IGP, e - EGP, ? - incomplete


Network Next Hop Metric LocPrf Weight Path

*> 200.1.0.0 0.0.0.0 0 32768 i

*> 200.1.1.0 0.0.0.0 0 32768 i

*> 200.1.2.0/23 0.0.0.0 0 32768 i





Correct Answer by Pavel Bykov about 9 years 8 months ago

If you want to advertise all four routes, do a:


router bgp 30x

!

network 200.1.0.0

network 200.1.1.0

no network 200.1.2.0 mask 255.255.254.0

network 200.1.2.0

network 200.1.3.0


aggregate-address 200.1.2.0 mask 255.255.254.0


neighbor providerA route-map Set_ASN_PA out

neighbor providerB route-map Set_ASN_PB out

!

!


ip prefix-list ProviderA seq 10 permit 200.1.0.0/23 ge 24

ip prefix-list ProviderA seq 20 permit 200.1.2.0/23


ip prefix-list ProviderB seq 10 permit 200.1.0.0/22 ge 24


route-map Set_ASN_PA permit 10

match ip address prefix-list ProviderA

!

route-map Set_ASN_PA permit 30

match as-path 130


route-map Set_ASN_PB permit 10

match ip address prefix-list ProviderB

!

route-map Set_ASN_PB permit 30

match as-path 130



This way, in routing table you will have /24 and /23 routes, but route-map will advertise only /24 to provider B, and /24 and /23 to provider A.

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Overall Rating: 5 (4 ratings)
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purohit_810 Wed, 07/18/2007 - 06:23
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You should use 200.1.0.0/22 Use.


It will conver your subnets


200.1.0.0/24

200.1.1.0/24

200.1.2.0/24

200.1.3.0/24


For 200.1.2.0/23, Advertise separately also. Because it covers more hosts than 200.1.2.0/24.


Or You can advertise that by Concept " periodic downloaded static route ".


Above routing table is true according to route aggregation.


Regards,

Dharmesh Purohit


Correct Answer
Pavel Bykov Wed, 07/18/2007 - 07:28
User Badges:
  • Silver, 250 points or more

If you want to advertise all four routes, do a:


router bgp 30x

!

network 200.1.0.0

network 200.1.1.0

no network 200.1.2.0 mask 255.255.254.0

network 200.1.2.0

network 200.1.3.0


aggregate-address 200.1.2.0 mask 255.255.254.0


neighbor providerA route-map Set_ASN_PA out

neighbor providerB route-map Set_ASN_PB out

!

!


ip prefix-list ProviderA seq 10 permit 200.1.0.0/23 ge 24

ip prefix-list ProviderA seq 20 permit 200.1.2.0/23


ip prefix-list ProviderB seq 10 permit 200.1.0.0/22 ge 24


route-map Set_ASN_PA permit 10

match ip address prefix-list ProviderA

!

route-map Set_ASN_PA permit 30

match as-path 130


route-map Set_ASN_PB permit 10

match ip address prefix-list ProviderB

!

route-map Set_ASN_PB permit 30

match as-path 130



This way, in routing table you will have /24 and /23 routes, but route-map will advertise only /24 to provider B, and /24 and /23 to provider A.

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