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Multiple BGP instance in one router

Hi ,

 

Is that possible to run multiple BGP instance in one router ? if not, why.? Please.

Ex:

Router BGP 500

Router BGP 600

3 Accepted Solutions

Accepted Solutions

Martin L
VIP
VIP

Yes, BGP does multiple BGP instances like IPv4 and IPv6, VRFs and VPNs can run on the same router under same BGP AS number;  those are called address families (address-family).

However, you can only run 1 BGP AS number on a router. you cannot enable BGP with different AS number if yo already running BGP.

 

Regards, ML
**Please Rate All Helpful Responses **

 

 

View solution in original post

Not like the way you have shown.

However, each router instance can run bgp with a different ASN. 

You can also use local-as for changing your AS with a neighbor e.g. for migrating purposes.

HTH.

View solution in original post

12 Replies 12

Martin L
VIP
VIP

Yes, BGP does multiple BGP instances like IPv4 and IPv6, VRFs and VPNs can run on the same router under same BGP AS number;  those are called address families (address-family).

However, you can only run 1 BGP AS number on a router. you cannot enable BGP with different AS number if yo already running BGP.

 

Regards, ML
**Please Rate All Helpful Responses **

 

 

Not like the way you have shown.

However, each router instance can run bgp with a different ASN. 

You can also use local-as for changing your AS with a neighbor e.g. for migrating purposes.

HTH.

On a side note, I searched for any software that actually does support multiple BGP instances on the same router. QUAGGA does, just in case anybody is interested...

 

https://www.nongnu.org/quagga/docs/docs-multi/BGP-instance-and-view.html

why we need BGP instance in router ?
the BGP design is multi instance (as I think ) by default.
for example 
I have one router with AS 100 it can connect to 
AS 100 ibgp 
AS 200 ebgp 
AS 300 ebgp 
AS 100 ibgp 

do show ip BGP you will see all prefix from different AS even if you us only AS in your Router.  

Thanks .

You are so so welcome 

jimgriffin
Level 1
Level 1

Was looking into this too. Need router to have completely separate routing tables for different vrf's. BGP on internet and we use BGP for different vendors and internal stuff that is not on the Internet. Was planning on a pair of routers that each handle Internet, WAN, and other routing. Would be surprising if even newer routers like Cat8500 can't have more than one totally independent BGP. 

can you more elaborate? I think you misunderstand bgp instance.

Just want to have the router act like several virtual routers. VRF has been around for a long time. But, Cisco routers limit to only one BGP AS number for the whole router, from what I have read here. No really clear answers. If vrf contexts can have separate static routes, why can't they each have their own BGP routing as well, having zero to do with other vrf's? We can't have just one AS number because that is usually something given to us, not something we can make up. 

I don't know precisely what you mean by a BGP "instance" and what you think I am misunderstanding.

 

thanks


Currently on ASR-1001-X:
toledo-router(config)#vrf definition hamburgers-vrf
toledo-router(config-vrf)#router bgp 60021
[error:] BGP is already running; AS is 64050

 

Want to do: (on newer router ??)
toledo-router(config)#vrf definition hamburgers-vrf
toledo-router(config-vrf)#router bgp 60021
address-family ipv4 ... etc

toledo-router(config)#vrf definition cheeseburgers-vrf
toledo-router(config-vrf)#router bgp 60022
address-family ipv4 ... etc

 

Cisco arbitrarily limits bgp to one AS. It is a decision on their part. What I am wondering is if the newer routers still do this or not. 

 

thanks

BGP is already running; AS is 64050 <- this error appear in any cisco router config one BGP but under it you can local-as "different for each neighbor"

https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13761-39.html

this link for this feature.

mmiljkovic
Level 1
Level 1

This is actually possible using ASR9000 routers.

As I remember 4 instance could ne used at the same time, but two instance is enough , for example, to move router from one MPLS domain to another...

 

https://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/asr9k-r6-2/routing/configuration/guide/b-routing-cg-asr9000-62x/b-routing-cg-asr9000-62x_chapter_010.html#concept_E6B1D3D6B8CA4742AED837B3A94E826F

 

Restrictions

  • The router supports maximum of 4 BGP instances.

  • Each BGP instance needs a unique router-id.

  • Only one Address Family can be configured under each BGP instance (VPNv4, VPNv6 and RT-Constrain can be configured under multiple BGP instances).

  • IPv4/IPv6 Unicast should be within the same BGP instance in which IPv4/IPv6 Labeled-Unicast is configured.

  • IPv4/IPv6 Multicast should be within the same BGP instance in which IPv4/IPv6 Unicast is configured.

  • All configuration changes for a single BGP instance can be committed together. However, configuration changes for multiple instances cannot be committed together.

  • Cisco recommends that BGP update-source should be unique in the default VRF over all instances while peering with the same remote router.

 

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