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BGP multihome issue

Inbound BGP load-balancing from same ISP routerBest practice for the combination of HSRP and ECMPImpact of IOS BGP soft-reconfiguration-inbound and peering optionsBGP - source routing breaking for some routesTwo ISP bgp topology?WAN connectivity down when BGP neighborship formedBYO thoughts on BGP routingBGP Route Dampaning - Not directly connected eBGP peers - EventsCisco BGP Graceful Restart behaviorlocal pref question

2

I have 2 different carriers on my router and I have set local preference to 350 for my first carrier to force it for my outbound traffic, and I set second carrier LP to 300.

I am receiving BGP full table from both providers.

My problem here is when my BGP session with carrier #1 disconnects, it takes about 5-10 minutes for the routes received from carrier #1 to be deleted from my routing table so to force my outbound to second carrier.
How can I solve this issue? Is there anyway when BGP session with carrier #1 disconnects, all routes are removed immediately ?

cisco routing bgp

share|improve this question

edited 8 hours ago

Ron Trunk

42.5k33989

asked 8 hours ago

BlackmetalBlackmetal

284

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Is it really 5-10 minutes, or is it 3 minutes (normal BGP timers)? When things stop working, it can seem like forever.
  
  – Ron Trunk
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  it takes about at least 5m, so whats your idea for solve this? how can if force immediately set next hop to my backup provider?
  
  – Blackmetal
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  A related question: If you prefer one carrier over the other, why are you receiving full routes? Why not a default route only? Processing 500,000 routes takes significant time, especially on a small router).
  
  – Ron Trunk
  6 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  You do not need the full routing table to have backups the way you describe; you only need default routes with different ADs. You could then have a faster failover.
  
  – Ron Maupin♦
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  A Cisco 2921, seriously? I'm amazed it's even able to hold 2 full tables. The root cause of your problems is that the CPU in those boxes are not able to cope with losing a full table. Either switch to defaults only (as was suggested in some answers) or upgrade to a model which was designed for this purpose.
  
  – Teun Vink♦
  4 hours ago
  

  
  
  
  

 | 
show 3 more comments

2

I have 2 different carriers on my router and I have set local preference to 350 for my first carrier to force it for my outbound traffic, and I set second carrier LP to 300.

I am receiving BGP full table from both providers.

My problem here is when my BGP session with carrier #1 disconnects, it takes about 5-10 minutes for the routes received from carrier #1 to be deleted from my routing table so to force my outbound to second carrier.
How can I solve this issue? Is there anyway when BGP session with carrier #1 disconnects, all routes are removed immediately ?

cisco routing bgp

share|improve this question

edited 8 hours ago

Ron Trunk

42.5k33989

asked 8 hours ago

BlackmetalBlackmetal

284

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Is it really 5-10 minutes, or is it 3 minutes (normal BGP timers)? When things stop working, it can seem like forever.
  
  – Ron Trunk
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  it takes about at least 5m, so whats your idea for solve this? how can if force immediately set next hop to my backup provider?
  
  – Blackmetal
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  A related question: If you prefer one carrier over the other, why are you receiving full routes? Why not a default route only? Processing 500,000 routes takes significant time, especially on a small router).
  
  – Ron Trunk
  6 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  You do not need the full routing table to have backups the way you describe; you only need default routes with different ADs. You could then have a faster failover.
  
  – Ron Maupin♦
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  A Cisco 2921, seriously? I'm amazed it's even able to hold 2 full tables. The root cause of your problems is that the CPU in those boxes are not able to cope with losing a full table. Either switch to defaults only (as was suggested in some answers) or upgrade to a model which was designed for this purpose.
  
  – Teun Vink♦
  4 hours ago
  

  
  
  
  

 | 
show 3 more comments

I have 2 different carriers on my router and I have set local preference to 350 for my first carrier to force it for my outbound traffic, and I set second carrier LP to 300.

I am receiving BGP full table from both providers.

My problem here is when my BGP session with carrier #1 disconnects, it takes about 5-10 minutes for the routes received from carrier #1 to be deleted from my routing table so to force my outbound to second carrier.
How can I solve this issue? Is there anyway when BGP session with carrier #1 disconnects, all routes are removed immediately ?

cisco routing bgp

share|improve this question

edited 8 hours ago

Ron Trunk

42.5k33989

asked 8 hours ago

BlackmetalBlackmetal

284

share|improve this question

edited 8 hours ago

Ron Trunk

42.5k33989

asked 8 hours ago

BlackmetalBlackmetal

284

share|improve this question

edited 8 hours ago

Ron Trunk

42.5k33989

asked 8 hours ago

BlackmetalBlackmetal

284

edited 8 hours ago

Ron Trunk

42.5k33989

edited 8 hours ago

Ron Trunk

42.5k33989

asked 8 hours ago

BlackmetalBlackmetal

284

asked 8 hours ago

BlackmetalBlackmetal

284

2 Answers
2

active

oldest

votes

5

There are two issues here:

1. BGP keepalives are 60 seconds, and the hold down timer is 3 times that. So that's your lower limit, unless you work with your carrier and adjust your timers. You both need to have the same timer values.




2. You are receiving full routes from both carriers. That's over 400,000 routes from each carrier. So your router needs to process that many entries when a carrier drops a session. That can take time on a small router like a 2900.

One idea is to only receive default routes from your carrier. You can still use local preference to prioritize carriers, but it's much faster to process one route than 400,000. Don't forget that you are still limited by #1.

share|improve this answer

answered 6 hours ago

Ron TrunkRon Trunk

42.5k33989

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Make that 770k routes per transit provider. BFD could help solve some of the issues with BGP hold timers.
  
  – Teun Vink♦
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  your mean is if i use local pref instead weight , it will process routes faster ? so in a case when one of my bgp session drop local pref change to second provider faster than weight atribute?
  
  – Blackmetal
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Blackmetal No. I assumed you meant local preference because of the value (350). Weight is usually a much higher value. But it's the same problem either way.
  
  – Ron Trunk
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  yes i know higher local pref will be better than weight, so if i use local pref i do not get faster route proccess when my bgp session disable?
  
  – Blackmetal
  5 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Neither one is faster. The problem is you have too many routes to process.
  
  – Ron Trunk
  5 hours ago
  

  
  
  
  

 | 
show 1 more comment

2

Another solution, as suggested by @ronmaupin 's comment, is to not accept any BGP routes at all and instead use static default routes (with different administrative distance for each ISP) along with object tracking.

You can ping an internal router of the ISP with IP SLA and use that to track the default route. That will fail over in a few seconds, instead of 3 minutes for BGP.

share|improve this answer

answered 5 hours ago

Ron TrunkRon Trunk

42.5k33989

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  i just tried change my parameter from weight to local prefrence and then shutdown my interface and i see right now it takes 1 minutes and 30 seconds for change to carrier 2! there is much difference between local pref and weight, anyone knows why ?
  
  – Blackmetal
  3 hours ago
  

  
  
  
  

add a comment | 

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5

There are two issues here:

1. BGP keepalives are 60 seconds, and the hold down timer is 3 times that. So that's your lower limit, unless you work with your carrier and adjust your timers. You both need to have the same timer values.




2. You are receiving full routes from both carriers. That's over 400,000 routes from each carrier. So your router needs to process that many entries when a carrier drops a session. That can take time on a small router like a 2900.

One idea is to only receive default routes from your carrier. You can still use local preference to prioritize carriers, but it's much faster to process one route than 400,000. Don't forget that you are still limited by #1.

share|improve this answer

answered 6 hours ago

Ron TrunkRon Trunk

42.5k33989

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Make that 770k routes per transit provider. BFD could help solve some of the issues with BGP hold timers.
  
  – Teun Vink♦
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  your mean is if i use local pref instead weight , it will process routes faster ? so in a case when one of my bgp session drop local pref change to second provider faster than weight atribute?
  
  – Blackmetal
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Blackmetal No. I assumed you meant local preference because of the value (350). Weight is usually a much higher value. But it's the same problem either way.
  
  – Ron Trunk
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  yes i know higher local pref will be better than weight, so if i use local pref i do not get faster route proccess when my bgp session disable?
  
  – Blackmetal
  5 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Neither one is faster. The problem is you have too many routes to process.
  
  – Ron Trunk
  5 hours ago
  

  
  
  
  

 | 
show 1 more comment

5

There are two issues here:

1. BGP keepalives are 60 seconds, and the hold down timer is 3 times that. So that's your lower limit, unless you work with your carrier and adjust your timers. You both need to have the same timer values.




2. You are receiving full routes from both carriers. That's over 400,000 routes from each carrier. So your router needs to process that many entries when a carrier drops a session. That can take time on a small router like a 2900.

One idea is to only receive default routes from your carrier. You can still use local preference to prioritize carriers, but it's much faster to process one route than 400,000. Don't forget that you are still limited by #1.

share|improve this answer

answered 6 hours ago

Ron TrunkRon Trunk

42.5k33989

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Make that 770k routes per transit provider. BFD could help solve some of the issues with BGP hold timers.
  
  – Teun Vink♦
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  your mean is if i use local pref instead weight , it will process routes faster ? so in a case when one of my bgp session drop local pref change to second provider faster than weight atribute?
  
  – Blackmetal
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Blackmetal No. I assumed you meant local preference because of the value (350). Weight is usually a much higher value. But it's the same problem either way.
  
  – Ron Trunk
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  yes i know higher local pref will be better than weight, so if i use local pref i do not get faster route proccess when my bgp session disable?
  
  – Blackmetal
  5 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Neither one is faster. The problem is you have too many routes to process.
  
  – Ron Trunk
  5 hours ago
  

  
  
  
  

 | 
show 1 more comment

There are two issues here:

1. BGP keepalives are 60 seconds, and the hold down timer is 3 times that. So that's your lower limit, unless you work with your carrier and adjust your timers. You both need to have the same timer values.




2. You are receiving full routes from both carriers. That's over 400,000 routes from each carrier. So your router needs to process that many entries when a carrier drops a session. That can take time on a small router like a 2900.

One idea is to only receive default routes from your carrier. You can still use local preference to prioritize carriers, but it's much faster to process one route than 400,000. Don't forget that you are still limited by #1.

share|improve this answer

answered 6 hours ago

Ron TrunkRon Trunk

42.5k33989

share|improve this answer

answered 6 hours ago

Ron TrunkRon Trunk

42.5k33989

answered 6 hours ago

Ron TrunkRon Trunk

42.5k33989

answered 6 hours ago

Ron TrunkRon Trunk

42.5k33989

2

Another solution, as suggested by @ronmaupin 's comment, is to not accept any BGP routes at all and instead use static default routes (with different administrative distance for each ISP) along with object tracking.

You can ping an internal router of the ISP with IP SLA and use that to track the default route. That will fail over in a few seconds, instead of 3 minutes for BGP.

share|improve this answer

answered 5 hours ago

Ron TrunkRon Trunk

42.5k33989

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  i just tried change my parameter from weight to local prefrence and then shutdown my interface and i see right now it takes 1 minutes and 30 seconds for change to carrier 2! there is much difference between local pref and weight, anyone knows why ?
  
  – Blackmetal
  3 hours ago
  

  
  
  
  

add a comment | 

2

Another solution, as suggested by @ronmaupin 's comment, is to not accept any BGP routes at all and instead use static default routes (with different administrative distance for each ISP) along with object tracking.

You can ping an internal router of the ISP with IP SLA and use that to track the default route. That will fail over in a few seconds, instead of 3 minutes for BGP.

share|improve this answer

answered 5 hours ago

Ron TrunkRon Trunk

42.5k33989

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  i just tried change my parameter from weight to local prefrence and then shutdown my interface and i see right now it takes 1 minutes and 30 seconds for change to carrier 2! there is much difference between local pref and weight, anyone knows why ?
  
  – Blackmetal
  3 hours ago
  

  
  
  
  

add a comment | 

Another solution, as suggested by @ronmaupin 's comment, is to not accept any BGP routes at all and instead use static default routes (with different administrative distance for each ISP) along with object tracking.

You can ping an internal router of the ISP with IP SLA and use that to track the default route. That will fail over in a few seconds, instead of 3 minutes for BGP.

share|improve this answer

answered 5 hours ago

Ron TrunkRon Trunk

42.5k33989

share|improve this answer

answered 5 hours ago

Ron TrunkRon Trunk

42.5k33989

answered 5 hours ago

Ron TrunkRon Trunk

42.5k33989

answered 5 hours ago

Ron TrunkRon Trunk

42.5k33989