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moods
 Post subject: BGP next-hop
PostPosted: Sun Jun 24, 2012 8:14 am 
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I am doing some labing today with BGP, and something is not clear to me.
I have 2 MPLS network connected to each other with within BGP address family vrf xx(for each vrf).

Router 7.7.7.7 is originating the prefix 70.70.70.70/32. My question is why routers 1.1.1.1 nad 2.2.2.2, for this prefix see the next hop of 111.111.111.111/222.222.222.222

I thought that next hop is not changed when doing iBGP updates...

Thanks for help


Attachments:
MPLS_BGP.jpg
MPLS_BGP.jpg [ 89.75 KiB | Viewed 531 times ]

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srg
 Post subject: Re: BGP next-hop
PostPosted: Sun Jun 24, 2012 8:47 am 
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next-hop-self on 111.111.111.111 and 222.222.222.222 towards 1.1.1.1 and 2.2.2.2?

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moods
 Post subject: Re: BGP next-hop
PostPosted: Sun Jun 24, 2012 12:08 pm 
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No:)

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mellowd
 Post subject: Re: BGP next-hop
PostPosted: Sun Jun 24, 2012 12:13 pm 
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Because you're doing some MPLS stuff. Let's have a look at the configs. What kind of MPLS you running?

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moods
 Post subject: Re: BGP next-hop
PostPosted: Sun Jun 24, 2012 12:57 pm 
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mellowd wrote:
Because you're doing some MPLS stuff. Let's have a look at the configs. What kind of MPLS you running?


Configs from which router?
Thanks for help

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mellowd
 Post subject: Re: BGP next-hop
PostPosted: Sun Jun 24, 2012 1:43 pm 
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Take 1.1.1.1, 222.222.222.222, and the internal MPLS routers for a start

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moods
 Post subject: Re: BGP next-hop
PostPosted: Sat Jul 07, 2012 2:40 am 
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Sorry for late reply

1.1.1.1
Code:
ip vrf A
 rd 65040:11
 route-target export 65040:11
 route-target import 65040:11
!
ip vrf B
 rd 65040:12
 route-target export 65040:12
 route-target import 65040:12
!

interface Loopback0
 ip address 1.1.1.1 255.255.255.255
!
interface Loopback11
 ip vrf forwarding A
 ip address 10.241.226.1 255.255.255.240
!
interface Loopback12
 ip vrf forwarding B
 ip address 10.241.224.1 255.255.255.240
!
!
interface GigabitEthernet0/0
 ip address 10.120.255.1 255.255.255.252
 carrier-delay msec 0
 duplex full
 speed 1000
 media-type gbic
 negotiation auto
 mpls ip
!
interface GigabitEthernet1/0
 no ip address
 shutdown
 negotiation auto
!
interface GigabitEthernet2/0
 no ip address
 shutdown
 negotiation auto
!
router ospf 1
 router-id 1.1.1.1
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0
!
router bgp 65040
 bgp router-id 1.1.1.1
 no bgp default ipv4-unicast
 bgp log-neighbor-changes
 neighbor 111.111.111.111 remote-as 65040
 neighbor 111.111.111.111 password CCIP
 neighbor 111.111.111.111 update-source Loopback0
 neighbor 222.222.222.222 remote-as 65040
 neighbor 222.222.222.222 password CCIP
 neighbor 222.222.222.222 update-source Loopback0
 !
 address-family ipv4
  no synchronization
  no auto-summary
 exit-address-family
 !
 address-family vpnv4
  neighbor 111.111.111.111 activate
  neighbor 111.111.111.111 send-community both
  neighbor 222.222.222.222 activate
  neighbor 222.222.222.222 send-community both
 exit-address-family
 !
 address-family ipv4 vrf A
  no synchronization
  redistribute connected
 exit-address-family
 !
 address-family ipv4 vrf B
  no synchronization
  redistribute connected
 exit-address-family


222.222.222.222

Code:
ip vrf C
 rd 65040:13
 route-target export 65040:13
 route-target import 65040:13
!
ip vrf A
 rd 65040:11
 route-target export 65040:11
 route-target import 65040:11
!
ip vrf B
 rd 65040:12
 route-target export 65040:12
 route-target import 65040:12
!

interface Loopback0
 ip address 222.222.222.222 255.255.255.255

!
interface GigabitEthernet0/0
 no ip address
 duplex full
 speed 1000
 media-type gbic
 negotiation auto
!         
interface GigabitEthernet0/0.111
 encapsulation dot1Q 111
 ip vrf forwarding A
 ip address 10.120.255.53 255.255.255.252
!
interface GigabitEthernet0/0.333
 encapsulation dot1Q 333
 ip vrf forwarding C
 ip address 10.120.255.57 255.255.255.252
!
interface GigabitEthernet1/0
 no ip address
 negotiation auto
!
interface GigabitEthernet1/0.12
 encapsulation dot1Q 12
 ip vrf forwarding B
 ip address 10.120.255.29 255.255.255.252
!
interface GigabitEthernet1/0.13
 encapsulation dot1Q 13
 ip vrf forwarding C
 ip address 10.120.255.33 255.255.255.252
!
interface GigabitEthernet2/0
 ip address 10.120.255.14 255.255.255.252
 carrier-delay msec 0
 negotiation auto
 mpls ip
!
interface GigabitEthernet3/0
 ip address 10.120.254.2 255.255.255.252
 ip ospf network point-to-point
 ip ospf 1 area 0
 carrier-delay msec 0
 negotiation auto
 mpls ip
!
router ospf 1
 log-adjacency-changes
 network 10.120.255.12 0.0.0.3 area 0
 network 222.222.222.222 0.0.0.0 area 0
!
router bgp 65040
 no bgp default ipv4-unicast
 bgp log-neighbor-changes
 neighbor 1.1.1.1 remote-as 65040
 neighbor 1.1.1.1 password CCIP
 neighbor 1.1.1.1 update-source Loopback0
 neighbor 2.2.2.2 remote-as 65040
 neighbor 2.2.2.2 password CCIP
 neighbor 2.2.2.2 update-source Loopback0
 neighbor 111.111.111.111 remote-as 65040
 neighbor 111.111.111.111 password CCIP
 neighbor 111.111.111.111 update-source Loopback0
 !
 address-family ipv4
  no synchronization
  no auto-summary
 exit-address-family
 !
 address-family vpnv4
  neighbor 1.1.1.1 activate
  neighbor 1.1.1.1 send-community both
  neighbor 1.1.1.1 route-reflector-client
  neighbor 2.2.2.2 activate
  neighbor 2.2.2.2 send-community both
  neighbor 2.2.2.2 route-reflector-client
  neighbor 111.111.111.111 activate
  neighbor 111.111.111.111 send-community both
  neighbor 111.111.111.111 route-reflector-client
 exit-address-family
 !
 address-family ipv4 vrf C
  no synchronization
  redistribute static
  neighbor 10.120.255.58 remote-as 65000
  neighbor 10.120.255.58 activate
 exit-address-family
 !
 address-family ipv4 vrf A
  no synchronization
  neighbor 10.120.255.54 remote-as 65000
  neighbor 10.120.255.54 activate
 exit-address-family
 !
 address-family ipv4 vrf B
  no synchronization
  redistribute static
 exit-address-family
!
ip forward-protocol nd
no ip http server
no ip http secure-server
!
!
ip route vrf C 13.13.13.13 255.255.255.255 10.120.255.34 250
ip route vrf B 66.66.66.66 255.255.255.255 GigabitEthernet1/0.12 10.120.255.30 250

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deadcow
 Post subject: Re: BGP next-hop
PostPosted: Sat Jul 07, 2012 8:32 am 
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http://www.cisco.com/en/US/docs/ios/12_ ... asleb.html

First of all from an academic standpoint this mpls routing between providers is not covered in CCiP. But than again it got retired . Now , if i got this right , where exactly do you see that next-hop ? Do you do an do sh ip route vrf X or a do sh ip route ? Because those 1.1.1.1 2.2.2.2 are mpls P edge routers and from a vrf point of view the packets are LFIB--CEF tag-switched. BGP just delivers the packets to their destination. You could have OSPF , RIP or whatever in the core. It doesn't matter. You have IGP (in your case IBGP) in the core that does nothing but provide connectivity and you have those BGP routers facing the AS exit points that translate those vrf's and redistribute them where they need to be. What I'm trying to say it's that this is how it should be. The mpls packets/frames (2.5) behave like this. Jesus my english is getting worse by the minute :)))

I think I can make it clearer if I would ask for you to look in the core. you have no vrf's and the routing table contains almoast nothing. so it's not a question of bgp advertizing in IBGP , it's just MPLS running over it.

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