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Bronze

MPLS IPVPN question

Hi everybody

 

I am learning IPVPN, specifically how we can use "as-override" to connect to remote ipvpn locations with just one AS; I encountered a strange situation described below:

 

 


        AS2                                              MPLS CLOUD AS1               AS2         
Soke2- f0/1--204.204.204.0/24--f0/1 PE4----R2----PE1-f1/0-- 105.105.105.0/24--f1/0-HUB5


spoke f0/1: 204.204.204.2
PE4 f0/1 : 204.204.204.4


PE f1/0: 105.105.105.1

HUB 5 f1/0: 105.105.105.5

 

We are using BGP between PE and CE

Above Spoke 2 is advertising 200.200.200.200/32 to HUB5 Via MPLS cloud ( PE4, R2,PE1, AS1)

Since spoke 2 and Hub both are in AS2, I have configured remove-as on PE1 so when PE1 advertises 200.200.200.200/32 to Hub5, it will replace AS 2 by AS1
 I expect Hub5 to learn 200.200.200.200/32 via ebgp but i do not understand why Hub5 has to advertise back 200.200.200.200/32 to PE1


HUB5#show ip route ( learning it from PE1)
B       200.200.200.2 [20/0] via 105.105.105.1, 01:04:54


Advertising back to PE1 (105.105.105.1)

HUB5#show ip bgp neighbors 105.105.105.1 advertised-routes
*> 200.200.200.2/32 105.105.105.1                          0 1 1 i


Configuration:

spoke2#show running-config | section bgp
router bgp 2
 no synchronization
 bgp log-neighbor-changes
 network 200.200.200.2 mask 255.255.255.255
 neighbor 204.204.204.4 remote-as 1

 

++++++++++++++


PE4#show running-config | section bgp
router bgp 1

Omitted!!
address-family ipv4 vrf Z
  neighbor 204.204.204.2 remote-as 2
  neighbor 204.204.204.2 activate
  neighbor 204.204.204.2 as-override
  no synchronization
 exit-address-family


PE1#show running-config | section bgp
router bgp 1

Omitted!!

address-family ipv4 vrf INSIDE
  neighbor 105.105.105.5 remote-as 2
  neighbor 105.105.105.5 activate
  neighbor 105.105.105.5 as-override
  no synchronization
 exit-address-family

 

HUB5#show running-config | section bgp
router bgp 2
 no synchronization
 bgp log-neighbor-changes
 
 neighbor 105.105.105.1 remote-as 1

 

thanks

 

 

 

3 REPLIES

Have you tried using a route

Have you tried using a route map?

Bronze

Hi Michael Thanks  for your

Hi Michael

 

Thanks  for your response. But I am confused why you mentioned route map.

 

 

 

I was reading another post

I was reading another post and accidentally replied to this one. Sorry for the confusion!

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