cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
263
Views
0
Helpful
5
Replies
DaeHeon Kang
Beginner

The question about configuration of MPBGP for MPLS VPN

I'd like to get clarify why the multiple same neighboring statements should be under each of commands, router bgp, address-family ipv4 and address-family vpnv4, as following configuration example. And what is the meaning that each neighboring statement under each of the multiple commands?

router bgp 1
bgp log-neighbor-changes
neighbor 10.200.254.2 remote-as 1                              <------  PE neighbor statement
neighbor 10.200.254.2 update-source Loopback0
!
address-family ipv4
redistribute rip
neighbor 10.200.254.2 activate          ...





send-community extended
exit-address-family

5 REPLIES 5
Francesco Molino
VIP Mentor

Hi 

BGP is a multiprotocol routing protocol. You can exchange information for ipv4, vpnv4, ipv6, ipv4 multicast, ... In order to get that working, you need to tell bgp under which "protocol" you want to exchange information that's why you need to specify the neighbor activation.

By default only ipv4-unicast is activated unless you configure no bgp default ipv4-unicast under bgp.

For example if you have ipv6 unicast address-family and you don't declare all neighbors that means you won't exchange ipv6 between all peers.

Hope  this clear.

PS: Please don't forget to rate and mark as correct answer if this answered your question 


Thanks
Francesco
PS: Please don't forget to rate and select as validated answer if this answered your question

Thanks for your answer.

But that is not really what I want to get clarify.. What mean does neighboring statement have under router bgp? And, what mean does the neighboring statement have under address-family vpnv4

The core that I want to know is that why I have to put the same neighboring statement under each router bgp and address-family vpnv4.

Hi

Vpnv4 is the protocol used between PE routers to exchange customers (CE) prefixes (prepended RD, and send RT bgp community) and labels information.

Then if you want to exchange all customer vrfs you'll need to activate neighbor under vpnv4 as well.

Is it more clear?

Thanks 

PS: Please don't forget to rate and mark as correct answer if this solved your issue 


Thanks
Francesco
PS: Please don't forget to rate and select as validated answer if this answered your question

I understand what function the neighboring statement does under the address-family vpnv4. It's relating to peering with PE and exchanging vpnv4 prefix. Then, what function the neighboring statement does under the router bgp?

router bgp 1
bgp log-neighbor-changes
neighbor 10.200.254.2 remote-as 1                              <--- why is this neighboring
neighbor 10.200.254.2 update-source Loopback0               statement should be define
!                                    ...








send-community extended
exit-address-family

The neighbor statement (in RED) in your post in define globally to BGP configuration to indicate the AS number. This has to be done globally because it would be equal doesn't matter which protocol you will activate for that neighbor.

Here the Cisco documentation:

Specifying a neighbor with an autonomous system number that matches the autonomous system number specified in the router bgp global configuration command identifies the neighbor as internal to the local autonomous system. Otherwise, the neighbor is considered external.

If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command.

By default, neighbors that are defined using the neighbor remote-as command in router configuration mode exchange only unicast address prefixes. To exchange other address prefix types, such as multicast and Virtual Private Network (VPN) Version 4, neighbors must also be activated using the neighbor activate command in address family configuration mode.

You can configure a neighbor under vpnv4 but it will be a private-as. Here a definition of private-as:

This command is available for external BGP (eBGP) neighbors only.

When an update is passed to the external neighbor, if the autonomous system path includes private autonomous system numbers, the software will drop the private autonomous system numbers.

If the autonomous system path includes both private and public autonomous system numbers, the software considers this to be a configuration error and does not remove the private autonomous system numbers.

If the autonomous system path contains the autonomous system number of the eBGP neighbor, the private autonomous system numbers will not be removed.

If this command is used with confederation, it will work as long as the private autonomous system numbers follow the confederation portion of the autonomous path.

The private autonomous system values are from 64512 to 65535.

I hope that this answer your question.

Thanks

PS: Please don't forget to rate and mark as correct answer if this solved your issue


Thanks
Francesco
PS: Please don't forget to rate and select as validated answer if this answered your question
Content for Community-Ad

This widget could not be displayed.