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gjohnson1963
Beginner

BGP AS-PATH PROBLEM

I trying to have all icomming traffic in from one IPS and the other as the fail over. I have all going out fine but incoming always uses the backup IPS which is a slower speed. What is missing?

router bgp 99999

no synchronization

bgp log-neighbor-changes

bgp dampening

network x.x.x.0

neighbor 69.xx.xx.xx remote-as 1111

neighbor 69.xx.xx.xx ebgp-multihop 3

neighbor 69.xx.xx.xx timers 10 30

neighbor 69.xx.xx.xx filter-list 2 in

neighbor 69.xx.xx.xx filter-list 3 out

neighbor 69.xx.xx.xx weight 2000

neighbor 144.xx.xx.xx remote-as 2222

neighbor 144.xx.xx.xx description Backup ISP

neighbor 144.xx.xx.xx timers 10 30

neighbor 144.xx.xx.xx route-map prepend out

neighbor 144.xx.xx.xx filter-list 1 in

neighbor 144.xx.xx.xx filter-list 3 out

neighbor 144.xx.xx.xx weight 100

no auto-summary

ip as-path access-list 1 permit ^2222_[0-9]*$

ip as-path access-list 2 permit ^1111_[0-9]*$

ip as-path access-list 3 permit ^$

route-map prepend permit 10

set as-path prepend 99999 99999 99999

21 REPLIES 21

Iam still waiting on my query from ISP regards to Route Dampening. But the ISPB (backup) do not support communitities...his reply..

"we are not currently offering community strings for BGP attributes. But if you want we can manually reduce the local preference of your prefixes on our access router."

Is it recomended to go with manual reduced Local pref on ISP end..?

Or work with ISP-A to advertise /25 & /25 instead of /24..?

please advice.

Thank you

MS

Hi,

My apologies about the Route Dampening update. You are mentioning Route Dampening from ISP-A (primary end).. is that correct...?

Becayuse on ISP-B end , we never bring down the link. Only on ISP-A end, for testing on HSRP, we pull the cable on orouter public interface. So ISP -A may be seeing the route failure, buu I believe, they are not dampening any routes, as when we put back the ISP_A cable, we have no issues in going online.

Only issues we have is... when I try to make ISP-B Active router (by pulling ISP-A public i/f cable) , then its taking 5-7 mins for the internet browseing to occur, even though ISP-B rtr takes the 'Active' role.

At this time, I think if IBGP is not needed between 2peers, then 'Synchronization' might be causing the issue.. not 100% sure though...

Any suggestions are appreciated.

Thank you in advacne

MS

Mehboob,

I was referring to BGP dampening on the back up ISP (ISP B). If this provider does use dampening, it could somehow cause the behavior you have seen.

Regards,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

Mehboob,

The manual configuration of the local preference would do the job.

The issue with advertising a /25 to ISP A is that most SP on the Internet will filter out prefixes /25 or longer. ISP A might accept it but its upstream might not.

Regards,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

Hi Harold,

Thank you very much for your information. Will update you after the test. It maight take few days..:-)

Thank you

MS

Question

One provider is sending partial routes the other sending default routes.

1. Is this a problem?

2. What would be the best option , both default or both partial .(Hardware 3640 128 meg )

George,

1. You may just end up sending more traffic on through the provider sending the partial. Not a problem if you do not reach the link capacity.

2. It depends on the providers but some of them will send you lots of routes even if they just send you partial routes. This could be a problem given that you only have 128MB of memory on this box. It also depends on what you are trying to achieve. Default from both providers may be just fine.

Regards,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México