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iBGP vs eBGP

Hello,

Understand how iBGP and eBGP work, can anyone tell me what are the pros and cons between these protocols? Any documentation is greatly appriciated.

Regards,

Joe

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Super Bronze

Re: iBGP vs eBGP

Disclaimer

The    Author of this posting offers the information contained within this    posting without consideration and with the reader's understanding that    there's no implied or expressed suitability or fitness for any  purpose.   Information provided is for informational purposes only and  should not   be construed as rendering professional advice of any kind.  Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In    no event shall Author be liable for any damages whatsoever  (including,   without limitation, damages for loss of use, data or  profit) arising  out  of the use or inability to use the posting's  information even if  Author  has been advised of the possibility of such  damage.

Posting

Joe Lee wrote:

Understand how iBGP and eBGP work, can anyone tell me what are the pros and cons between these protocols? Any documentation is greatly appriciated.

If you understand how both work, then you realize the determinant is whether to BGP peers are using the same AS or a different AS.  For routine eBGP, you're peers are very likely to use different ASs, so you wouldn't have a choice.  For internal BGP usage, I suppose you could use different (private?) ASs, down to individual BGP peers allowing them to operate with eBGP rules.

The pros and cons of using eBGP internally vs. iBGP would be due to the differences in peering rules and routing rules.  With eBGP rules you don't need to create a full mesh as you do with iBGP (or reflectors or confederations).  With eBGP rules, you're less likely to require another IGP if the peers share a common subnet, or if they don't, need special multi-hop configuration along with extra routing information external to BGP itself.  With eBGP rules, AS hops might indicate actual best path.

Although in theory I guess you could use eBGP rules with private ASs within the same logical AS, it could make it difficult to peer with more then one external public AS.  In other words, this isn't normally a choice, so curious how you envisioned using pros and cons to select between eBGP vs. iBGP.

PS:

NB: "***" = Plural of AS - AS.s (sigh - politically correct word filtering)

6 REPLIES
VIP Super Bronze

iBGP vs eBGP

Hi Joe,

IBGP is usually is used within an autonomous system. It is basically Internal BGP vs EBGP is used for one autonomous system to connect to another autonomous system (External BGP).

http://www.skullbox.net/bgp.php

HTH

iBGP vs eBGP

Hi Joe,

Each other are there for different aspects.
iBGP is to serve within AS where eBGP is to serve between different autonomous system.
If an AS has multiple BGP speakers, the AS can serve as a transit service for other ASs.


Please rate the helpfull posts.
Regards,
Naidu.

Super Bronze

Re: iBGP vs eBGP

Disclaimer

The    Author of this posting offers the information contained within this    posting without consideration and with the reader's understanding that    there's no implied or expressed suitability or fitness for any  purpose.   Information provided is for informational purposes only and  should not   be construed as rendering professional advice of any kind.  Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In    no event shall Author be liable for any damages whatsoever  (including,   without limitation, damages for loss of use, data or  profit) arising  out  of the use or inability to use the posting's  information even if  Author  has been advised of the possibility of such  damage.

Posting

Joe Lee wrote:

Understand how iBGP and eBGP work, can anyone tell me what are the pros and cons between these protocols? Any documentation is greatly appriciated.

If you understand how both work, then you realize the determinant is whether to BGP peers are using the same AS or a different AS.  For routine eBGP, you're peers are very likely to use different ASs, so you wouldn't have a choice.  For internal BGP usage, I suppose you could use different (private?) ASs, down to individual BGP peers allowing them to operate with eBGP rules.

The pros and cons of using eBGP internally vs. iBGP would be due to the differences in peering rules and routing rules.  With eBGP rules you don't need to create a full mesh as you do with iBGP (or reflectors or confederations).  With eBGP rules, you're less likely to require another IGP if the peers share a common subnet, or if they don't, need special multi-hop configuration along with extra routing information external to BGP itself.  With eBGP rules, AS hops might indicate actual best path.

Although in theory I guess you could use eBGP rules with private ASs within the same logical AS, it could make it difficult to peer with more then one external public AS.  In other words, this isn't normally a choice, so curious how you envisioned using pros and cons to select between eBGP vs. iBGP.

PS:

NB: "***" = Plural of AS - AS.s (sigh - politically correct word filtering)

iBGP vs eBGP

Hi,

Understand how iBGP and eBGP work, can anyone tell me what are the pros and cons between these protocols?

there is only one protocol in fact - BGP.

There are just eBGP and iBGP neigbors.

And different rules how prefixes received from  eBGP/iBGP are treated and sent to other neighbors.

See

http://www.cisco.com/en/US/customer/tech/tk365/technologies_q_and_a_item09186a00800949e8.shtml#nineteen

for examples.

HTH,

Milan

New Member

4 years old - WOW

4 years old - WOW

Is there a different site people are going to now?

Oh yeah - I agree with Milan.

Super Bronze

Postings on this site go back

Postings on this site go back much further than even 4 years; mine go back to 2007, some other still active posters go back several years further.

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