Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

BGP DMZ Link bandwidth

Hello,


As Cisco official documentation says, The Border Gateway Protocol (BGP) Link Bandwidth  feature is used to advertise the bandwidth of an autonomous system exit  link as an extended community.

If we configure the AS in such a way that even the iBGP peers will know about the 2 possible routes for one prefix, doing unequal cost load balancing, how do they know what is the load of the interface ? They receive at some hello time interval information about the interface utilization through the usage of extended communities ?

Documentation says BGP is doing load balancing, and load balancing means balancing the packets according to interface utilization/load.

Thanks in advance for replying !

  • LAN Switching and Routing
Everyone's tags (4)
11 REPLIES
New Member

BGP DMZ Link bandwidth

hi Alex,

who knows you might find this link useful:

http://bit.ly/ayyrKY

http://bit.ly/LebRQn

regards,

New Member

BGP DMZ Link bandwidth

Thanks, but replying to a question with 'read the RFC' or an INE technical tutorial is not a good answer you know...

New Member

BGP DMZ Link bandwidth

are you having trouble with your bgp config, or you just learn the feature for certification?

Gold

BGP DMZ Link bandwidth

Hi Alex,

If we configure the AS in such a way that even the iBGP peers will know about the 2 possible routes for one prefix, doing unequal cost load balancing, how do they know what is the load of the interface ? They receive at some hello time interval information about the interface utilization through the usage of extended communities ?

Documentation says BGP is doing load balancing, and load balancing means balancing the packets according to interface utilization/load.

First, Load Balancing does NOT mean balancing the packets according to interface Load, as you said above.

it means Balancing the Traffic Load across multiple paths.

Now your answer:

The BGP Link Bandwidth feature allows BGP to be configured to send traffic over multiple iBGP or eBGP learned paths where the traffic that is sent is proportional to the bandwidth of the links that are used to exit the autonomous system. well, in this scenario there's nowhere that a link's load has effect on routing.

plz Rate if it helped.

Soroush,

Hope it Helps, Soroush.
New Member

BGP DMZ Link bandwidth

Load balancing means balancing the packets according to interface load/utilization. Balancing the traffic load accross different multiple paths is called load sharing. Load balancing and load sharing are 2 things people usually don't differentiate and come to wrong definition. There is one video by this guy who is one of the few 5xCCIE and he is explaining the difference between load sharing and load balancing, even though the video is not related to BGP -->  http://goo.gl/L84ag. Same confusion also takes place for EIGRP, where the definition calls it unequal cost load balancing, but when you check the routes you will see there one line saying "traffic share count".

Now according to Cisco documentation,  "This feature is used with BGP multipath features to configure load balancing over links with unequal bandwidth. " Since load balancing is balancing the traffic according to interface load, back to the beginning, my question still remains: how do the peers know about the interface load of other peers(especially iBGP peers).

New Member

BGP DMZ Link bandwidth

hi Alex,

the bandwidth terms on internal routing protocol or BGP are only used for the metric. with this metric, the routing protocol can take the decision (routing), it doesnot take the actual troughput information from the interface.

i believe the terms load balancing on cisco docs according to this feature is reffering to load sharing. bgp dont do load balancing.

if what youre looking for is more "concept" question when you learning something, i would recomend http://learningnetwork.cisco.com, there you can find good answers. if you having a real issue with bgp on your production router, i believe this forum is the best place for looking answers.

regards,

New Member

BGP DMZ Link bandwidth

Hi handoko,

This is what I also think, that there is just a gap in the documentation, and they should reffer to load sharing the traffic, not load balancing. They should call it load sharing based on configured bandwidth of the links to peers.

Gold

Re: BGP DMZ Link bandwidth

btw, Load balancing means, balancing the traffic sharing according to a measure i.e.: Bandwidth. not necessarily LOAD of THE LINK.

   Benefits of the BGP Link Bandwidth Feature

The BGP Link Bandwidth feature allows BGP to be configured to send traffic over multiple iBGP or eBGP learned paths where the traffic that is sent is proportional to the bandwidth of the links that are used to exit the autonomous system. The configuration of this feature can be used with eBGP and iBGP multipath features to enable unequal cost load balancing over multiple links. Unequal cost load balancing over links with unequal bandwidth was not possible in BGP before the BGP Link Bandwidth feature was introduced.


http://www.cisco.com/en/US/docs/ios/12_2t/12_2t2/feature/guide/ftbgplb.html#wp1058357

plz Rate if it helped,

Soroush.

Hope it Helps, Soroush.
New Member

BGP DMZ Link bandwidth

Ok guys.. I am trying to get a real and serious answer in here, we all know you're trying to get as many points as possible, by looking at your other posts, but answering to questions with copy-paste and official documentation links is not that helpful.

I am still waiting for other opinions from some advanced users.

1857
Views
5
Helpful
11
Replies
This widget could not be displayed.