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Regarding eBGP Multipath

Inbound BGP load-balancing from same ISP routerBGP - how does IGP know the right route?Quagga bgp advertisment stop after peer restartQuagga not announcing external routes over ibgp sessionBYO thoughts on BGP routingStruggling inbound and outbound traffic engineering to/from iBGP peers at different POPsRegarding ECMP hashing

1

In one of the blogs, i read:

"Unlike most routing protocols, BGP only selects a single best path for each prefix. It doesn’t do ECMP (Equal Cost Multi-Path Routing) by default but it is possible to enable this.

In order for BGP to use the second path, the following attributes have to match:

Weight

Local Preference

AS Path (both AS number and AS path length)

Origin code

MED

IGP metric

Also, the next hop address for each path must be different. This comes into play when you are multihomed to the same router."

Que:
Even if all the above attributes match, will the "Router ID" (choose the one with lowest router-id) not be used as a tie-breaker ?

bgp multipath

share|improve this question

asked 8 hours ago

fsocietyfsociety

498521

add a comment | 

1

In one of the blogs, i read:

"Unlike most routing protocols, BGP only selects a single best path for each prefix. It doesn’t do ECMP (Equal Cost Multi-Path Routing) by default but it is possible to enable this.

In order for BGP to use the second path, the following attributes have to match:

Weight

Local Preference

AS Path (both AS number and AS path length)

Origin code

MED

IGP metric

Also, the next hop address for each path must be different. This comes into play when you are multihomed to the same router."

Que:
Even if all the above attributes match, will the "Router ID" (choose the one with lowest router-id) not be used as a tie-breaker ?

bgp multipath

share|improve this question

asked 8 hours ago

fsocietyfsociety

498521

add a comment | 

In one of the blogs, i read:

"Unlike most routing protocols, BGP only selects a single best path for each prefix. It doesn’t do ECMP (Equal Cost Multi-Path Routing) by default but it is possible to enable this.

In order for BGP to use the second path, the following attributes have to match:

Weight

Local Preference

AS Path (both AS number and AS path length)

Origin code

MED

IGP metric

Also, the next hop address for each path must be different. This comes into play when you are multihomed to the same router."

Que:
Even if all the above attributes match, will the "Router ID" (choose the one with lowest router-id) not be used as a tie-breaker ?

bgp multipath

share|improve this question

asked 8 hours ago

fsocietyfsociety

498521

Weight

Local Preference

AS Path (both AS number and AS path length)

Origin code

MED

IGP metric

Also, the next hop address for each path must be different. This comes into play when you are multihomed to the same router."

share|improve this question

asked 8 hours ago

fsocietyfsociety

498521

share|improve this question

asked 8 hours ago

fsocietyfsociety

498521

asked 8 hours ago

fsocietyfsociety

498521

asked 8 hours ago

fsocietyfsociety

498521

1 Answer
1

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4

If you enable ECMP, the router ID will not be used as tie breaker, because that would defeat the purpose. If all those attributes match, routes are considered to be equal and you can utilise all links with matching attributes.

share|improve this answer

answered 8 hours ago

Teun Vink♦Teun Vink

12.2k53354

add a comment | 

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4

If you enable ECMP, the router ID will not be used as tie breaker, because that would defeat the purpose. If all those attributes match, routes are considered to be equal and you can utilise all links with matching attributes.

share|improve this answer

answered 8 hours ago

Teun Vink♦Teun Vink

12.2k53354

add a comment | 

4

If you enable ECMP, the router ID will not be used as tie breaker, because that would defeat the purpose. If all those attributes match, routes are considered to be equal and you can utilise all links with matching attributes.

share|improve this answer

answered 8 hours ago

Teun Vink♦Teun Vink

12.2k53354

add a comment | 

If you enable ECMP, the router ID will not be used as tie breaker, because that would defeat the purpose. If all those attributes match, routes are considered to be equal and you can utilise all links with matching attributes.

share|improve this answer

answered 8 hours ago

Teun Vink♦Teun Vink

12.2k53354

share|improve this answer

answered 8 hours ago

Teun Vink♦Teun Vink

12.2k53354

answered 8 hours ago

Teun Vink♦Teun Vink

12.2k53354

answered 8 hours ago

Teun Vink♦Teun Vink

12.2k53354