topic Re: BGP Multihoming - different providers in Switching

BGP Multihoming - different providers

ilnaiduccna — Wed, 06 Mar 2019 16:42:55 GMT

Hi Experts,

As of now we have single internet provider to my DC and we have public IP pool (195.34.56.0/24 leased from old provider)
Now we take another internet provider for redundancy and we bought one public IP pool (193.141.24.0/24)

I have two my routers (1841) in hsrp at my DC, both providers have their own routers at perimeter network at my DC.

Both new and Old internet lines are ready to use, now I have to do BGP multihoming on my both hsrp routers and I dont want use IP pool 195.34.56.0 which taking leased from old provider.

At present I have my own two public IP pools those are 193.141.24.0/24 and 193.143.209/20

Experts can someone guide me how I have to proceed with Mutlihoming and what are the steps I have to follow and how to configure and all...

Thanks in advance.

Regards,
Naidu.

Re: BGP Multihoming - different providers

Giuseppe Larosa — Tue, 24 Nov 2009 13:53:04 GMT

Hello Naidu,

I hope you are well.

if you have your own public IP blocks you are fine

use the following example for BGP multihoming

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00800945bf.shtml

Hope to help

Giuseppe

Re: BGP Multihoming - different providers

ilnaiduccna — Wed, 25 Nov 2009 14:16:56 GMT

Hi Giuseppe,

Thanks for your response.

I too have the same document, what I would like to request you is if you have experienced in BGP multihoming and I want your best suggestions how to go towards success on this.

Can you provide me If you have any kind of templete.

Thanks & Regards,

Naidu.

Re: BGP Multihoming - different providers

Giuseppe Larosa — Wed, 25 Nov 2009 18:11:20 GMT

Hello Naidu,

some safety measures have to be added :

use route filters to decide what you are willing to accept from each provider.

use an as path access-list to be sure you will never act as a transit between the two providers

example:

you want to accept only a default route

ip prefix-list only-default permit 0.0.0.0/0

route-map fromISP1 permit 10

match ip address prefix only-default

route-map fromISP2 permit 10

match ip address prefix only-default

ip as-path access-list 11 permit ^$

route-map toISP1 permit 10

match as-path 11

route-map toISP2 permit 10

match as-path 11

router bgp your.ASN

neigh ISP1.ipaddress route-map fromISP1 in

neigh ISP1.ipaddress route-map toISP1 out

neigh ISP2.ipaddress route-map fromISP2 in

neigh ISP2.ipaddress route-map toISP2 out

It is better to have separated route-maps you may want to make changes in the future

Hope to help

Giuseppe

Re: BGP Multihoming - different providers

ilnaiduccna — Thu, 26 Nov 2009 10:33:03 GMT

Hi Guiseppe,

Nice to see your reply and good explanation .

As of now the BGP multihoming configured and maintain will be by Provider itself.

Yes, I would like to point only default route to provider GW.

say 0.0.0.0 0.0.0.0 197.28.56.1

I hope the ip as-path access-list can configure on my routers, to not accept any other AS from internet; is that right?

I couldn't understand......

you want to accept only a default route

ip prefix-list only-default permit 0.0.0.0/0

You mean shall I accept default route, which means the whole default route from internet?

Please correct me if I am wrong.

Thanks in advance,

Regards,

Naidu.

Re: BGP Multihoming - different providers

Giuseppe Larosa — Thu, 26 Nov 2009 11:26:35 GMT

Hello Naidu,

yes the idea is to accept a BGP route 0.0.0.0/0 that is a default route from providers routers

using a default static route is not recommended because your router cannot know when one router has a problem (indirect failure)

your router sends your public IP blocks and you receive a default BGP route

Hope to help

Giuseppe

Re: BGP Multihoming - different providers

ilnaiduccna — Thu, 26 Nov 2009 14:19:50 GMT

Hi Giuseppe,

Oh....great...!

I have small doubts.

If we accept a default route from providers, will it be not accept like whole internet routing table like that?

If that is not the case, I heard sometimes the whole internet routing table will land on our routers then router get crash like that because of some miss configuration; is that right?

In what situations will be like that happen, what could be the causes to came whole internet routing table to our router?

Is there any specific BGP default route like that? (yes the idea is to accept a BGP route 0.0.0.0/0 that is a default route from providers routers)

Can you please clear me.

Thanks & Regards,

Naidu.

Re: BGP Multihoming - different providers

Giuseppe Larosa — Thu, 26 Nov 2009 14:40:29 GMT

Hello Naidu,

the proposed input route filter has the objective to accept only the default route that is a single BGP prefix.

a full routing table is made of 300,000 routes nowdays and cannot be handled by your router.

accepting a default route means accepting only special prefix 0.0.0.0/0 as I wrote so your router shouldn't be overhwhelmed by it.

Hope to help

Giuseppe

Re: BGP Multihoming - different providers

Athiqur Rahman — Wed, 07 Apr 2010 15:11:02 GMT

Hi Giuseppe,

picking up on your point about not adding a default static route but to accept static route from ISP. In multi homed network how would you make it so the one ISP is higher priority and used as default exit point. If the main ISP fails then the default gateway should be to the second ISP?

Thanks

Re: BGP Multihoming - different providers

Tulsi Ram Puttaraju — Wed, 07 Apr 2010 19:47:10 GMT

Hi,

You can set the your preferences in your neighbor route-map out

route-map RouteMAP_Name

 match ip address 1

 set local-preference 25

 set metric 127

 set weight 30000

 set next-hop 192.92.68.24

 set origin igp

Any of the parameter above.

http://www.ciscosystems.com/en/US/docs/ios/12_0/np1/configuration/guide/1cbgp.html#wp6018

Thanks,